I personally feel that it's about as comfortable as it can get for a handheld computer. I may have bigger hands than most, but ergonomically it just works for me. I've been pleasantly surprised by almost all of the aspects of the P1. I read waaaay too much into the complaints of posters (here) before I bought the device. I would agree with Grench though, that making the "P2" a bit more slimmer would allow for even more freedom - stowing in an upper pocket or something. I guess that you're never going to please everyone, but the P1 was/is an impressive machine for all that it does.
The only way that it could get better, is to reduce the weight some...make it slimmer...OR have a radical redesign which would make the unit even more balanced. Something like a PSP 2000/Vita, where the screen is in the "middle" of the unit. The gaming controls would have to be on the left/right sides...and the "keyboard" would have to be a "iCP2" ("connected via bluetooth), or a physically attached keyboard that folds backwards underneath the unit. Ergonomically, that would feel the most comfortable I guess for "gamers"...