@john: Ok. Just curious, can you tell me which trackball implementation have you tried and how long have you spent with said trackball to get yourself acquainted with how it works?

On my Bold and G1, the OS+trackball has been tweaked to offer the precision required that I've never had any problem with getting the cursor to move in the direction intended or the number of single clicks required out of it.

And as for the conveniene issue (as you've mentioned), I think that can be put aside, as there's no stylus anymore in new devices nowadays

After comparing the use of trackball and d-pad on handhelds, i've found them to be very similar actually:
- Conversion of the free 360' direction of the trackball to 4 primary d-pad direction is never a problem. Never got them wrong, once.
- The movements are usually either a staccato string of single clicks (very similarly duplicated on trackballs) or when you need it repeated for a short duration (moving the cursor\pointer for a few rows or columns (of icon or letters) at a time you either hold the d-pad down to let the key-press repeat work on its own or scroll the trackball having a bit of control on the speed of its repetition. For 90% of common document manipulation and interface interaction, they're really sufficient.

The main difference (to me) is for playing games when you need to hold the d-pad button down for long periods of time and that cannot be easily replicated on a trackball.

I've spent 15 minutes with the digital mouse on the raon, I don't think it is really useable.