For the sleep tracking component, or just in general?
Personally I have no problems charging my watch daily, just like my phone. But it does present an issue if you want to wear it while sleeping. I've never wanted to wear a watch sleeping though...
As a complete side note, i've been impressed by the battery life. I haven't gone below 50% in a day yet, and I have so little concern that I will I took battery percentage off of my watch face.
Battery life. Apple Watch will improve over time, but it's nowhere near there yet when it can't be worn overnight.