right... for mobile use, one-handed finger usage is essential, and a small set of hardware keys (d-pad) is the best interface for this as you don't even have to look at the device when operating it.

a touchscreen based interface cannot provide this, finger-friendly or not, as it lacks the tactile feedback. you cannot feel the "OK" button when you slide over it.
more important though, all tablets so far were much too big and heavy for me to consider them for any mobile use case. they're too big for my trousers, too heavy for my shirt.

that's why i think maemo UI work should focus more on the couch and restaurant use cases than on the "walk in the park"-ones. the couch use case is when you take the device not only to skip a track, but to do something with it for 20min or more. surfing, chatting, working through your mail,... these are the strengths of the tablets, and it's a lot easier to perform such tasks over a longer period of time with an efficient, high-precision input device.

(of course, maybe the next device will be as small as my phone.... i could see me taking it to the park, then. i still wouldn't use a touchscreen, though, only hardware keys.)