Keep in mind when you're in the states (U.S.) that you'll only be able to use the EVDO/3G and and not the UMTS portion from the sim. Verizon has this locked down for preventing users to not being able to stick a ATT Sim to use their 3G network i.e. not including the frequency bands that they use So they have rogue customers trying to buy their products to use on a different network.
Now if you go Abroad, it is then , you'll be able to use the GSM/UMTS in area's that don't have CDMA and have it work.
Some say that the unlocking may be the same when the Storm comes out, but only time will tell when the device comes out and can be tested, but keep in mind, in theory if it does work when someone tests it, Verizon will probably removed the frequency band for UMTS which means you'll only be able to use EDGE if you stick in a ATT sim, or Tmo sim. (Tmo will probably don't work either way cuz they use a different 3G frequency)
Mobile/PDA Support Engineer