Tablet PC Buzz forum member charlesalexander has one of the development kits for Apple's OSX on Intel hardware. He decided to see what would happen if he loaded the image on his Toshiba M200 Tablet PC.
He ran into some problems but he also got some things working. Here's a quote form the post.
Still the screen of the tablet itself didn't work. After much reading on OS X's monitor configuration I set about building a config file for the tablet screen. It turned out to be easy enough, I just had to bypass the plug-n-play and hardcode the settings.
Screen rotation, the network card, wireless, the modem, USB, the touchpad, and I'm sure plenty of other stuff isn't working. But with apple's inkwell ( http://www.apple.com/macosx/features/inkwell/ ) this thing is really showing potential. After messing around with this thing for a few days I can't believe apple themselves never released a tablet.
Here's a link to the full post.