Sorry if this has been covered before, but I am new to smartphones. The Eris only has CDMA, so it won't be able to connect to 3G in Europe, for example. But will it be able to connect to open wi-fi networks?
I've had wifi on for a long time, wifi doesn't really eat much battery life at all. GPS will though. The only bad thing about wifi is if you have yahoo mail accounts, they won't get sync'd, it has something to do with yahoo knowing that it's not a phone IP address or something similar to that.