On some phones (usually unbranded high-end ones) like the N95, you can choose 3G-only mode so it can't fall back to 2G when signal is low. This can greatly help in fringe areas because otherwise, in dual-mode 3/2G, usually the phone can switch down to 2G well before you are out of range. My BlackBerry 9700 can be switched like this via the engineering menu & I no longer have these premature fallbacks. I heard the 9000 can do the same too.
2007-05-14: T-Mobile post-paid (USA: 267)
2007-12: T-Mobile pre-paid (USA: 857)
2009-01-21: Mobal World (UK)
2010-06-08: TracFone (USA: 215)
2011-03-12: Tru (USA: 305)
2011-08-01: AT&T pre-paid (USA: 212)
2011-08-22: Spot Mobile (USA: 603)