2 yrs ago: Palm Centro on Sprint (SERO)
Now: Evo on Sprint (EPRP)
1 yr from now: AT&T or Verizon, the only two carriers with decent coverage in my part of Maine.
Since Sprint has a roaming contract with Verizon, the above makes no sense. When you don't have Sprint coverage, you default to Verizon.
Then: G1 on TMobile
Now: ThunderBolt on Verizon