I think the iPad is a step in an interesting direction, but is still not the Next Big Thing that will change the way we play.
Regarding battery life, the Next Big Thing in display tech, combining the energy efficiency and direct sunlight readability of e-paper with the vivid colour and fast refresh rate of LCDs, actually isn't too far away either, from what I've read in some of the professional journals (in electrical engineering) that I get.
For me, that would make me seriously look at something like the iPad as a new iteration from having the books at the table. The big thing for me is that a backlit screen fatigues my eyes after a while. It's why I can stand reading for long periods at a time off of a screen. However, if something had the sunlight readability of epaper, that would be a serious game changer for me.
Right now, I would seriously consider getting an iPad if I were still going to conventions on a regular basis. Carrying around a small iPad everywhere would be a lot more convenient than carrying around a backpack full of books. And my laptop doesn't solve that problem for me, because I hate reading PDFs off of a laptop. PDF documents are too hard to browse with a laptop and trackpad. Just that small step of being able to touch the screen to browse, grab, and enlarge makes a big difference.
So, I'd love an iPad for convention going. It'd be perfect.
Another thing that I would love an iPad for at the gaming table is just the ability to pick it up and pan it around. I go to DeviantArt.com a lot for pictures of NPCs and the like. However, picking up my laptop and panning it around for everyone to see is just this side of awkward. It would be totally different if I could just hold it up like a clipboard (particularly because it's light as well). Also, I could just pass it around the table. Plus, I use a lot of music in my games, so I could just hook up some speakers to the iPad, so it would double as my music player.
However, I'm not willing to spend 500$ for all of those frills. If I'm going to spend that much, I'd want at least a camera and USB port on my iPad. But I have no doubt those things are coming.