It's funny, I bought the iPad 3G with the idea of replacing my laptop. As it turns out, the software just isn't there- both on Apple's part and on the part of third-party developers.
But what I did find is that it's replacing my iPhone in many situations. I still use my iPhone to check email on the go and browse the web (and recently, I use both to read books on the Kindle app, it's pretty awesome). But when I want to play a quick game or look up a recipe or get Google map directions (things I used to whip out my iPhone 3GS to take care of), I gravitate towards my iPad. The screen size and app interfaces are much easier to use and interact with.
I'm also ready to dump AT&T. It depends, on this point, on waiting until one or two of the contracts on my family plan expire in early fall so I won't be stuck with a $500 termination fee. I had no problem, and I lived with drop-calls without any issue, but once they instituted a relatively-low 2GB data cap on the iPad data plan, I was livid.
My thinking is this: if I only use my iPhone for web browsing, checking and composing quick emails, Google Maps (and the like), and other quick games and utilities, I could use any Android device. I wouldn't even notice a difference, to be honest. And Sprint's tethering package is a better deal than the iPad 3G: you turn your phone into a WiFi hotspot (your laptop, iPad, or any other device can use its data) for $30/month with a 5GB data cap on top of unlimited data the phone itself uses. And if you're in a 4G area, even though there's a $10/month premium on the phone data plan, there is no data cap at all for tethering. You can stream as many Netflix movies as you want, without having to downsample them over 3G, for one flat rate.
To be honest, I'd dump AT&T right now and pay the fee, except I've only heard horrible things about the EVO 4G battery life. Like it borders on the unusable- I'll wait until the Android 2.2 update gets pushed over the next few weeks and see if it improves.
Anyway, with my iPad, I don't really need an iPhone- just a nice phone with a nice app store and good web browsing capabilities. Android fits the bill, and Sprint saves me a ton of money per month, with more minutes and people on my plan with data, and no caps (at least, none yet).