It's a beautiful phone and I'd love to use it without a case, but I know that I'll end up dropping it at some point. The case on my M8 has the scars to prove it.
The only thing I'm really missing so far is Blinkfeed. I used that quite a lot on my M8, so I'll have to find a replacement for it. Other than that though, I'm really happy that I made the jump to the 6P.