I just got the Ultra last Wednesday and I'm pretty happy with it. I ended up fully charging it the first night because I wanted to start with a full battery. I think I got a little over 24 hours on battery but I can't recall for sure. I did get 40 hours and a couple minutes the other day. Just light use with some texting, games, web browsing, and just playing around with the features. The back doesn't feel slippery at all to me. The back is smooth but I can see how some will think of it being slippery. I've always had screen protectors on my phones. Hopefully I shouldn't need one with the gorilla glass. I'm not sure how strong the Kevlar back is so it's up in the air if I should buy a case. I like the display and how the colors really stand out. I'm coming from a blackberry so everything is much better compared to my old phone. I'm not a big picture taker so the camera is fine by my standards. Played around with the ok google now voice commands for a bit and it works pretty good.