You can unlock the 2.2.1 if it is with the older modem firmware , which means that you have upgraded with the custom firmware instead of official apple firmware 2.2.1
If its with the new firmware&baseband you will only be able to unlock it with a sim card like this one
http://www.unlockediphone.info
If you get an iphone with the new firmware 3.0 , who knows when you will be able to unlock and jailbreak it. Maybe never?
I would rather have an working iphone than the new but locked one.