First off, no, you should not.
Now, assuming you're an American, the difference is that here in Europe we use different frequencies for mobile service. You will likely be able to use an EU phone in the US (depending on your network), but you'll probably only get a 3G connection and may suffer a weaker signal.
Aside from that it's too expensive. It launched at $399 and you can get a new 3T for $439.