I've been using my iPad for a little bit over a month now, and I am really pleased. It certainly is a luxury item; no defined need that it meets, but it's a lot of fun. Plus it is so lightweight to carry around, it can easily substitute for a laptop when you don't need to do any serious typing or editing (which means I can use it a bit for work, but not that much).
My favorite uses so far are watching recorded tv shows or movies, reading books (very good for that; so far I alternate between the Amazon Kindle and the Barnes&Noble Nook apps), checking my email and news headlines, and playing some time-wasting games.
It's fairly hard to imagine it - you really need to play with one. Apple has run some commercials that give you an idea of what it's like, but they are speedy:
All in all, it is a great consumer entertainment device.