how does it handle Installtion of other apps?
The pdaXrom package manager system frontend is reasonable to look at, but the version of ipkg is fragile and doesn't handle failed installs well. It's a step or three back from the OZ ipkg imho. However, depending on what you want to install, it does do the job.
I'm used to using the package manager on opie OZ, but the gpe OZ doesn't seem to have an option to use other feeds (or not one that I've noticed).
FYI with your 5500, I've never used the GUI package manager on GPE, but I understand that it's not that great. You'd be better off using ipkg on the command line (because it works fine, feeds can be added - which may then be accessible from the GUI package manager). This might not be what you want, but it does work.
Do things seem to install smoothly without hitches most of the time? I run into problems where something like mplayer will just say 'error' while trying to install it.
I had troubles installing old pdaXrom apps (and other X11 apps) due to missing symbols errors, however as Vanguard says, there's a new feed for pdaXrom apps, and presumably a toolchain from which compiled apps will work (so it's possible to re-compile what doesn't work).
Regardsing your mplayer errors; you will receive the same non-descriptive style of error with pdaXrom (or any other ROM for that matter) if a file doesn't want to install unless you increase the verbosity level (or run from the command line).
Regards,
Simon
P.S. Regarding your toubles with GPE - post in the OZ section of the forum (as I feel that I'm talking a bit OT here) and we'll see if we can get you sorted.