Unimpressed
I've tried a friend's Galaxy Tab; they were rather miffed I wasn't completely impressed.
It's *way* overpriced for 470 quid, never mind 550. The screen is gorgeous, but several buttons are hard to see black rubber on a black case - FAIL.
The Android sites may offer a wide variety of software, but my first attempts (Doom and Quake) didn't work correctly and it's not as easy to kill programs on Android. Angry Birds worked fine but pops up adverts as you play. I did try an impressive FPS, but frankly I'd prefer a mouse..
We did manage to get it to hang at least once, the OS is clearly a scaled up Phone OS rather than a cut down desktop OS, and whilst it's basically usable for reading e-books on, the Kindle is several orders of magnitude better.
Basically it doesn't seem to do anything spectacularly well.
For the same cost you could buy a Kindle (e-book), cheap tablet (web browsing) and a Nintendo DS (games). Multi device, yes, but each one better than the Galaxy Tab and you'd have change left over too.