That itself isn't a problem. It's probably part of the recipe for awesome, week-plus battery lives. But the band itself, while fitting fine on my wrist when brand new, started to degrade quickly.
To be clear: the electronics are fine. The rubber enclosure seems to have expanded up to the point where the button was completely covered by it. Upon "folding" the end so one could access the button, the rubber continued to extend, etc.
Finally, maybe eight months in, the button snapped out. I can't use a lot of the functions of the band now, such as exercise/run tracking; I can't even tell it _when_ I'm going to bed, although the app still auto-discovers when I was sleeping.
When the band starts to vibrate (unless it's my half-hour inactivity buzz), you can either stick with it for two solid minutes or plug it into the app.
The main reason I still wear it is that the motion-aware/light sleep estimate-cognizant wake-up alarm is the only way to live. It's the snooze button rebooted: rather than waking up to hit a button and then enjoying some more light sleep, the band will just wake you up when you're already semi-awake.
TL;DR: this band broke down very soon after purchase but even as it does a fraction of its original functions it's really really cool.