I just picked up a Kensington Slim Type today (the white Mac one) and am enjoying it tremendously. I am typing on it right now, in fact, with it hooked up to my 12" Pbook
There are differences between the Pbook and the Slim Type. The Slim Type has F keys up to F15, which is initially a bit strange after being used to maxing out at F12... Plus, it means, for now until I get used to it, I need to look down to find F12 on the keyboard. I have noticed that it is right below the last of the seven silver multimedia buttons at the top
Also, on the right hand side, to the left of the arrow keys, there are CTRL and Insert/HELP keys which you don't find on the Pbook. For me, this makes my fingers stretch out a bit more when 1) I want to switch between Tabs in Safari by pressing Apple + Shift + Arrow Left/Right, and 2) jump to the end or beginning of a line while typing by pressing Apple + Arrow Left/Right. Strange, but something that I am sure I will eventually get used to.
I think that's it. I love the keyboard and am very happy I picked it up. Highly recommended.
If you have got any more questions just ask and I'll try my best to respond.