Battery life is very good, I get about 18-20 hours with average use and about 10-12 hours with heavy use (compare this to my previous Nexus 4 & Galaxy S3 and you're talking about somewhere in the range of 30% better battery life with the One). With light usage I've easily seen 24-26+ hours before charging. To sum it up, I charge my phone once a day on average (unplug at 6:00am and plug in around 11:00pm with 20-30% battery remaining).
Sense 5 is a refreshing change from TouchWiz, IMO I prefer it even over stock Android. Simple, easy to use, fast, functional. Blinkfeed is a innovative change from having to use several widgets for a fraction of the same information. Imagine a Flipboard-like home screen.
Phone is fast, I mean no lag - whatsoever. I run some pretty intensive Live Wallpapers and it never affects the speed of the phone. Call reception is great, sound is incredible (you can't find better sound in a mobile device, period). Screen is stunning. Crisp, accurate colors and sharp text at any size. 100% hands down the best phone I've ever had. IMO the best phone available, period.