I have an older tablet, a Fujitsu Stylistic 3400. It's a P3, 400mhz, upgraded the hard drive to 20 gig, running XP Pro. It works pretty well, I'm using it primarily as an MP3 player for my car. The passive touch screen works wonders when driving! It's nice to just tap the "next" button in Winamp, or browse through the playlist without looking at a tiny MP3 player display. Heck, the thing even saved Tom's party after Battlecry
Overall they're cool things, although the handwriting recognition isn't quite perfect (not sure how it is in XP Tablet Edition, haven't had the chance to install it yet). In any case, definitely worth it if you jot down a lot of quick notes, or like the idea of carrying around a laptop like a book. Much easier to work and move at the same time.