Well, to me the iPad is just a large iPhone, and I already have one.
Except the iPad, as far as I currently know, is different in the ways that it is stronger than the iPhone and one thing I totally love is that iWorks is coming for it. I would have loved if iWork could come with a pen-use in Pages, so you could actually use the iPad for taking notes in school, using an "iPen" instead of the nice onscreen keyboard, but it would require Pages to be able to convert your handwritten letters into computer fonts. Would not be that hard, but will it sell?
In any case I would be interested in using the iPad in school and on the go in trains, even though I do own a nice Macbook pro.
The iPad is more of a transportable computer than the iPhone, which to me makes the big difference. I predict a bright future for the iPad. Having worked in a bookstore for some years I give it more credit as to the future of eBooks.
Carrying around a heavy book on the train or on your journey will be made so much more comfortable when you have your book collection in your under 1kg heavy iPad. A small problem with eBooks on screen is the brightness of the page, which can be dealt with using a more matt paper background than the usual white on computer screens, more relaxing for the eye.
I would love to own an iPad, but I will wait for now.
Say it did in a few years come with a cam in the front, so you could use it for messenger programs, my favorite being iChat.
I do not know if it can now, but if not, then add the ability for Pages and Numbers to print using either WiFi printer or a USB cable. See now you have a full computer for everything; well at least for the most common day to day tasks. And with all those Apps, even more fun.
So to me the iPad lacks at least one thing for now, a build-in iSight, mic not needed, you get the same head set as for the iPhone.
And to top that an iChat App please
Last, if it is not already in it, the ability to print. As you have already made a nice dock with keyboard, why not go that one step further...
In closing, I will probably only consider buying an iPad once there is an iSight build into it and hopefully an iChat App on AppStore.
So if you have those and Pages can print, then it only need to be able to use internet banking and I would buy one for my mom, unless I already bought her an iMac for her upcoming 50 year birthday. Bringing her into the Mac family as well, sad is that her accountancy program does not work with Mac unless I install Windows on it, and no way in hell I will infect it.