i have some issues/grips with the gsm phone system, i'm not sure if they qualify as problems or not. the gsm system has some really advance call handling built into the network - whereas the competition doesn't even have these capabilities at all.
[1] dual lines. it's built into the gsm system and all gsm phones. to date, i think only one european vendor offers a dual-line plan. i'd much rather carry around one phone, not two (one personal, one business).
while this is not for everyone, i there's a huge segment out there would pick up a second line if they didn't have to carry a second phone. the vendors would sell more lines too. especially considering it more commonplace for people to dump their analog land lines these days.
there is one advantage having two phones, being able to use gmrs data on one, while simultaneously talking on the other. it's unclear if something like that would be possible on a single phone. certainly not on my phone, espcially if i used a headset (my phone only supports one active bluetooth connection - and one gmrs or voice call at a time for that matter).
that's more likely my phone's fault.
[2] on a similar note there are advanced call management features for incoming faxes. you can, in theory, route incoming fax calls -- the problem is the system doesn't differentiate the incoming call as a fax call until you connect, and at that point, you are 'talking' to a fax machine and it really doesn't matter what you've set up for fax calls.
i used to have a second line assigned through voicestream/t-mobile, that service worked pretty well, until they changed their voicemail system and it didn't really so much.
never mind that anyway -- the best solution was to get a separate fax line with a service that emails tiff images. even a dedicated line is cheaper than what cell phone vendors offer.