My parents recently upgraded their phones. They didn't want to pay a lot for them, so they opted to just get some Nokias (the
5300, I think) which were $50 with a contract extension. So I was showing off Google Maps to my dad on my W580i, and he wondered if he could run it on his Nokia. I figured he could, so I put my SIM into his phone so I could download
Google Maps Mobile, which downloaded and installed just fine.
However, the phone doesn't allow applications to do network stuff by default; you have to grant access to an application for that purpose. Unfortunately, T-Mobile has disabled the option to grant network access to applications. Clearly T-Mobile just wants to restrict people to only using the craptacular network stuff they deem appropriate for mobile use, rather than allowing them to actually make use of their network access.
I have a feeling when my contract is up I will be switching to a pay-as-you-go service. Unfortunately, T-Mobile is the only one with PAYG rates which make sense, and no useful data service whatsoever (you can only access T-Zones, which is little more than a ringtone purchase portal at this point). AT&T supposedly has data service on PAYG but they're completely unclear on the details, and their PAYG voice rates are confusing and byzantine.
1:57 PM I found unbranding instructions which should make it so that you can run any Java app without restrictions.