As a user of Psion palmtops for some years, I see some things that can be improved. Symbian (Psion/EPOC developers) has published an excellent style guide: EIKON Application Style Guide. This document sums up many years of experience in GUI design on small devices.

I'd say the vertical scrollbar is the most important to keep, as it would be hard to quickly jump up and down without it. A more important change is to move the arrow buttons to one end (or both ends) of the scrollbar (like in some KDE themes). This makes it much easier to operate with the pen (most devices will probably have a touch screen). There can be a similar button pair for horizontal scrolling, but without the scroll bar.

Some things are unnecessary to keep on the screen. The menu should be hidden, accessible by a button (has worked nicely for ten years on Psion PDAs). Toolbars should be simple (like on the screenshots you've shown). All buttons should also be large enough to operate with a finger.

Regards,
 Gaute Hvoslef Kvalnes