I've seen some on-hands reviews of the S4, where they demonstrated the the motion controls.....and they looked abit laggy.
Specifically, one of the guys demonstrating the phone waved his hand across the front of the phone to page flip....but required him to do it several times, at the right speed, for it to pick up.
Cool functionality, but I'm not sure how graceful the tech is.
Also, there has been some questions raised about the barometer & humidity. Considering many folks will keep the device in their pocket / purse...or strapped to their body during workouts....how accurate & valuable will that info be?
In addition, will the Hall sensor location be problematic for folks that accidently cover it with their hand, or with other non-S cover cases?