BUT, be careful what you wish for.
Before you go, take a trip to your local AT&T office and purchase their Europe package, the one that includes data.
Failure to do that will result in you owing AT&T a fortune at your next billing.
Without the package, when your iPhone checks for mail, or mail is pushed to the phone, it will be making an international call to the US and the data download price, per kb, will be measured in Dollars!
The phone itself will work without the plan but will also be expensive.
If the apps phone home, or require internet access, then these too will cost you lots, without the package.
Of course, if you are in a WiFi hotspot, there is not data charge.
I am going to be traveling in Spain and Germany in the near future. I have a G3 Iphone and want to know if the APPs and email will work.