Review: Samsung DoubleTime for AT&T
The DoubleTime runs all the stock Android 2.2 messaging applications, and doesn't offer anything new or unique.
It has the generic email app for POP/IMAP/Exchange email, and the dedicated Gmail application for Google users. Both of these applications are capable and time-tested.
The stock SMS/MMS app is loaded on the DoubleTime, and I didn't notice any different or unusual behavior with it. It offers threaded conversations, as always.
As for IM, the DoubleTime has GTalk on board, and nothing else. If you use Yahoo, Windows Live or AIM, you'll have to seek out third-party apps from the Android Market.
On the social networking front, the DoubleTime is preloaded with Facebook, but nothing else. if you want Twitter or any other social networking services you'll have to hit up the Android Market.