Just like my M4 my Series 2 is a daily wearer
! Use it all the time for workouts more bike than running and besides a timepiece it gets used next most frequently for apple pay - use it all over the place and feels weird now when I for any reason am not wearing it when at a pay station! 3rd most use is a tie between acknowledging or responding to texts or adjusting music volume/selection.
For ref I went with a Series 1 when launched and after a week sent it back - faulty battery I suspect but Apple never really admitted as such but did refund. Waited for some time after Series 2 launch and enough feedback to warrant a second go and have to say overall quite happy - battery life is a full day plus, occasionally up to 2 days, in normal use - less than a day when used heavily in work outs.
PS: Not sure what Series 3 adds re fitness tracking but Series 2 is fairly comprehensive in this respect. That and the data you can potentially share with your Doc is an interesting potential upside.