It looks good, with Apple's current slimmed-down shiny black and aluminium aesthetic. It's too heavy to hold up with one hand in use -- it's either two hands or rest it on your lap. This turns out not to be much of a problem.
Steve Jobs was right to say that it's a game-changer. It makes browsing the web into a whole new experience -- it's more tactile, and the screen is the perfect size for web browsing. Safari is lacking some handy features, but Atomic Web costs 59p and provides useful things like adblock and opening links in background tabs. All web browsers really need some way to scroll individual elements in a web page as well as the page as a whole, though.
There are already a lot of good apps, which make use of the larger screen. Compared with the iPhone, the screen is large enough that an app can have different parts of the screen that do different things. My current most-used apps are Goodreader (excellent PDF reader), iBooks (Apple's own eBook reader), NetNewsWire (RSS reader with Google Reader synchronization), IM+ (chat) and Plants versus Zombies (game).
Photographs look stunning on the screen, and there are a bunch of apps like Guardian Eyewitness, APOD and FlickStackr that take advantage of this.
The keyboard is about as good as a touch keyboard could be. I can easily do my usual two finger plus thumb typing in it. It could do with an apostrophe on the main keyboard, although I eventually discovered that you can get one by pressing and holding on the comma. Still, I'd rather see a couple of extra keys replacing the right-hand numeric shift key. I'm typing this review actually on the iPad, and it doesn't feel much slower than on a real keyboard.
One of my main reasons for buying it was for reading eBooks, and it has some way to go here. The screen is actually too big for eBooks, and the only two reader apps that give you two columns in landscape mode at present are iBooks (which is a pain to get your own books into) and Barnes & Noble eReader, which is only available in the US and appears to be impossible to get your one books into. I'm sure a better app will be along soon, preferably with Calibre integration.
The battery life is astonishing. We were away for a couple of days at the weekend, and I didn't need to take the charger. The claimed 10 hours seems like a bit of an under-estimate, even when playing CPU-intensive games.