If I buy a new, unlocked cell phone... does theat mean I can take the SIM card from my current phone, put it in the new one, and immediately start using that new cell phone? I'm considering one of the new high end phones like the Motorola Razr V3 or the Sony Ericsson S710.. right now I have a nokia 7210.. and im just considering the option of buying the new one unlocked instead of from my provider... also, what do you guys think of those phones? are there any others that you would recommend?
Thanks

As I understand it, it should work fine. Both those phones are nice ones. I'm gonna pick up the Motorola V635 in a few weeks, which may not be as fancy as either of those two, but still has a great bang for the buck.

yes you can place your sim card into any unlocked phone.
I suggest waiting just one more month as the new batch of high end phones will be out.
Wait two to three if you want the new Apple/Motorola iTunes phone.