I have the S2 with 3g capabilities. I had the S1. S2 blows S1 out of the water for me. Better design. More reliable, gps on board for going running. ...
Do you have the bluetooth or 3g/4g version? My 3g/4g version might make it a day and a half but I've never tested that theory cause I charge it every night anyway.
For what it is worth... calls forwarded from my AT&T work phone go right through, no problem. Calls from my sprint phone take a long time to reach the watch. Its on Sprint's end I believe.
I like having a potential 2-3 day battery because it gives me a better chance of making it through a day without charging. Has nothing to do with sleeping Roth the watch for me.