As the old saying goes: If it isn't broke, don't fix it. I've worked with one GSM carrier (T-Mobile), one TDMA carrier (Cellular One), and one CDMA carrier (VZW) and CDMA is by far the most impressive of the lot. TDMA isn't even worth looking at...all the major TDMA carriers are frantically switching to GSM, and this is going to cause MAJOR issues with the network.

To put it simply, "rigging" a TDMA system to be GSM (which is what AWS did, and you can see the results of this) is the equivalent of using a wire hanger to hold your exhaust pipe in place.

GSM, while a fine system, is inherently limited. The fact that it has to be transposed into a CDMA hybrid just to reach semi-3G status should tell you you're better off sticking with CDMA. (The only true 3G system has been defined as 3XRTT, only available on CDMA networks).

CDMA is having its growing pains right now, no doubt. EV-DO won't increase the voice quality, unfortunately, but EV-DV will. Give CDMA a few years to grow and develop (Sprint and VZW), and there won't be a comparison. Japan is the most technically advanced country in the world, and their major carrier DoCoMo (as well as all the others) favor CDMA beyond anything.