Everyone is hesitating: shall I buy the iPad WiFi only version or the iPad which has 3G as well?
I can't determine how you live and I can't decide what iPad (WiFi-only or WiFi+3G) you are going to buy but I can help as much as I can.
Why (not) to choose for the iPad 3G...
GPS and cellular in the iPad 3G
The iPad 3G includes a GPS and is able to connect to a 3G network. If you are travelling a lot and you are planning to use your iPad about everywhere - for example in a car or at work - than the ability to have internet everywhere would be great. If you are planning to use your iPad as a big TomTom, than GPS would be nice as well. Note that your iPad will increase in size: in height about 0,3 milimetre and in width about 0,1 milimetre.
Personal living situation: 'WiFi everywhere'
Think about your personal living situation. There's a big chance you've got WiFi at home where you will probably use it most of the time. When you go somewhere else, there will probably be an open WiFi network (like at the Mc Donalds, but also just in cities). And what about work? There probably is WiFi too over there. And let's assume you've got a smartphone with internet acces. If you are travelling in, let's say, a car. What will you do earlier? Get your iPad to check a webpage, or quickly get your smartphone to browse the web. You probably won't browse the web all the time, but you will also use apps... and not all of them require an internet connection. This is a quote I posted earlier in a topic over here, which goes further into this.
The black strip
This will be different for each and everyone of us. Some may like the black strip on the iPad, and others may not like. You might think about the 'good old times' when the iPhone was just launched. Just remember that this black strip is also visible at the front of your iPad.
The price: $15 or $30 for internet on GRPS, EDGE and 3G
No contract. Just $15 or $30 a month for 250 mb and unlimited internet. Internet everywhere for a solid price without a contract. Everywhere you will find internet with this cheap 3G plan. And if there's no 3G, than you will fall back on EDGE and if necessary even GRPS.
The price for the iPad 3G: +$130.
To get 3G and GPS you need to pay an extra $130. This is pretty expensive, especially when you compare it like this:
Re-sale value
If you are planning to get iPad Revision 2 (R2) next year, than you will probably sell your iPad. You will get more money for a WiFi+3G model than for a WiFi-only model. Though, you should think about the fact if people are willing to pay for it next year.
No nation wide coverage
Remember you won't find 3G all through-out the nation. Sure, when there's no 3G the connection it might fall back on EDGE or GRPS but are you willing to wait a long time to load an internet webpage? EDGE and GRPS are really slow compared to 3G and 3G-coverage isn't very good yet.
So, what iPad model should I get?
That's totally up to you. Again: look at your personal situation. There's WiFi kinda everywhere now a days, and what will you do faster? Get your smartphone and browse the web, or your iPad while you're travelling? You should decide for your self, but I hope you now have 'a better vision' on what to do.

I can't determine how you live and I can't decide what iPad (WiFi-only or WiFi+3G) you are going to buy but I can help as much as I can.
Why (not) to choose for the iPad 3G...
GPS and cellular in the iPad 3G
The iPad 3G includes a GPS and is able to connect to a 3G network. If you are travelling a lot and you are planning to use your iPad about everywhere - for example in a car or at work - than the ability to have internet everywhere would be great. If you are planning to use your iPad as a big TomTom, than GPS would be nice as well. Note that your iPad will increase in size: in height about 0,3 milimetre and in width about 0,1 milimetre.
Personal living situation: 'WiFi everywhere'
Think about your personal living situation. There's a big chance you've got WiFi at home where you will probably use it most of the time. When you go somewhere else, there will probably be an open WiFi network (like at the Mc Donalds, but also just in cities). And what about work? There probably is WiFi too over there. And let's assume you've got a smartphone with internet acces. If you are travelling in, let's say, a car. What will you do earlier? Get your iPad to check a webpage, or quickly get your smartphone to browse the web. You probably won't browse the web all the time, but you will also use apps... and not all of them require an internet connection. This is a quote I posted earlier in a topic over here, which goes further into this.
It's maybe better to spend an extra $130 if you really want a 3G connection. You should think how you are actually going to use it. Are you bringing your iPad everywhere? Or are you only going to use it at home, work etc. (where you will usually find a WiFi network).I have a 64gb Wi-Fi on pre-order and a 64gb Wi-Fi + 3G on pre-order.
I just can't decide which order to cancel yet. See, I only get EDGE in the part of Maine that I live in, but, I'm moving to Montreal for four years over the summer. And there's obviously 3G up there. It's just a matter of when a Canadian provider will offer Micro-SIM cards up there.
Ugh, I can't decide what to do. It'd probably be best to just spend the extra $130 and wait a little longer to get the iPad that will work best for me come late Summer and through the year. Or, shoot, I don't know. Haha. I'm terrible at these decisions.
Either way, I'm getting an iPad. Heck yes!
And if you are sitting next to the driver in a car, what will you do faster (assuming you've got an iPhone)? Pick up your iPhone and open a webpage, or get your iPad?
Think about how and where you are going to use it. And if you've got an iPhone, what you will do faster for quickly checking a webpage when you are travelling: get your iPad, or get your iPhone?
Personally I'm going for the wifi only version. I will use it mostly at home, but sometimes I will bring it with me and if I'm somewhere else there's usually some (open) wifi network. If I bring it with me when I'm sitting next to the drive when we're going abroad or something like that, than it's more likely that I will use some apps and watch a movie. If I quickly want to check the internet, I will just pick my iPhone and browse het web.
And than there's another thing. I don't know if this is the case in the USA, but over here in NL I got free wifi hotspots via my iPhone carrier (and it's partner's wifi hotspots) all across the country and even at airports. So if I want to use my iPad and want to go on the internet I can just check if there's a wifi hotspot of my carrier or it's partners and I will use that wifi hotspot.
The onliest moment I can think of where there is no WiFi, is in the car or in rural areas. But than again, you won't find a very good 3G connection - if you find one at all - in rural areas.
So, the WiFi only version saves me $130 already plus the extra subscriptions for the 3G connection. Next to that, I don't really like the black strip which is also visible at the front of the iPad).
The black strip
This will be different for each and everyone of us. Some may like the black strip on the iPad, and others may not like. You might think about the 'good old times' when the iPhone was just launched. Just remember that this black strip is also visible at the front of your iPad.
The price: $15 or $30 for internet on GRPS, EDGE and 3G
No contract. Just $15 or $30 a month for 250 mb and unlimited internet. Internet everywhere for a solid price without a contract. Everywhere you will find internet with this cheap 3G plan. And if there's no 3G, than you will fall back on EDGE and if necessary even GRPS.
The price for the iPad 3G: +$130.
To get 3G and GPS you need to pay an extra $130. This is pretty expensive, especially when you compare it like this:
If you want to have GPS and 3G (number 3) than you should pay another $130 to model number 1 but that's without doubling the capacity. If you leave out 3G and GPS, but you pay 'just' another $100 you will double the capacity (number 2).1) WiFi-only iPad 16 GB: $499
2) WiFi-only iPad 32 GB: $599
3) WiFi+3G iPad 16 GB: $629
Re-sale value
If you are planning to get iPad Revision 2 (R2) next year, than you will probably sell your iPad. You will get more money for a WiFi+3G model than for a WiFi-only model. Though, you should think about the fact if people are willing to pay for it next year.
No nation wide coverage
Remember you won't find 3G all through-out the nation. Sure, when there's no 3G the connection it might fall back on EDGE or GRPS but are you willing to wait a long time to load an internet webpage? EDGE and GRPS are really slow compared to 3G and 3G-coverage isn't very good yet.
So, what iPad model should I get?
That's totally up to you. Again: look at your personal situation. There's WiFi kinda everywhere now a days, and what will you do faster? Get your smartphone and browse the web, or your iPad while you're travelling? You should decide for your self, but I hope you now have 'a better vision' on what to do.