However, the trackball on the Pearl is rather dependent on thumb operation, especially when working one handed. I found that it was very difficult for me to transfer right-handed reflexes to my left - which at one point led me to deleting mail off the Pearl that I'd rather have left on the device... I suspect that the same would have been true for anyone going from left to right as well, but it's an user interface quirk that I hadn't expected.
In other news I'm slowly beginning to pick up on the keypad shortcuts for navigation, only to come a cropper when an application doesn't support them. Newsgator's pocket RSS reader is an excellent application (which keeps in sync with my desktop reader), but you need to use the trackball to scroll through pages rather than using the familiar "3" and "9" page up/page down short cuts. Instead the keys move you between articles. Inconsistent use of system short cuts is not a good idea.
I've also been able to turn some of these thoughts into a magazine column, so that's an unexpected usage!