That's pretty excessive battery drain. I've had mine on for 9 hours so far and it is at 64% (also the 38mm). Are you tracking activities such as running? That will drain the battery pretty quickly.
Did you install apps and set it all up? When I was setting mine up, the battery dropped fast, I think if you use it a lot, and in an intensive way, the battery will drop fast.
If you your a moderate user, the battery is very good.
Yes I installed around 10 apps. That only took 2 minutes though. After that I played with the apps for around 15 minutes, and that's it. For the rest of the time it was sleeping with occasional wakes and swiping through glances.