John Carmack has recently added an entry on his cell phone adventures. His use of J2ME seemed fairly frustrating, but he points out that Qualcomm's BREW looks promising. It would be interesting to find out if he's tried the .NET Compact Framework which I believe has support for the 3D graphics accelerator found in HTC's Feeler (marketed as O2 Xphone II - similar to HTC's Typhoon, aka Orange SPV C500, but targetted for gaming). From what I understand, unlike J2ME, the .NET Compact Framework does act as a WORA platform.
Amongst other things, he discusses a problem for multi-player games - long thought to be a "killer app" for 3G phones. Firstly he points out one problem: 2" screens limit the immersive experience. Secondly he describes the problems that will arise due to the high latency of packet communication technologies including current 3G infrastructure. Basically, unless you want to play some turn-based game, low latency circuit-switched communications is necessary even though the throughput can be very low. This could be very expensive if the game lasts several hours. This will remain true for some time. However, there is some hope. Many US operators (including this recent Verizon timetable) plan VoIP across EV-DO Revision A: 2008 or 2009 for Verizon, early 2007 for Sprint. Using some of the protocols including QoS specification in Rev. A, these network upgrades should be capable of providing the desired low latency.