Considering I travel alot (by car.. due to my self employed business), I am simply loving the GPS or navigation system. Previous phone was Samsung Instinct, which is a mediocre phone itself and an decent GPS, this blows it wide open. I don't care really about the Mp3 or audio part of the phone as that's not why I got it, but am looking forward to watching movies too on this thing.
The car racing game (haha) included is just STUNNING. For me, a 43 year old, this device is a ipod, xbox, wii (etc) replacement. In fact, I already listed those devices online for sale.
Oh, even made a call on the Epic (haha), and sounds terrific. There isn't anything I don't like yet about it. I did make sure I bought a car charger for it. That was the only extra I really needed.
Facebook works well. Had a little trouble getting used to the mobile version, but 10 minutes later, I was good to go.