I've had a 4GB/64GB Unit for about 2 weeks now. I'm not one of the official reviewers for AC, but here are my thoughts so far:
Ergonomics - Pretty good for a 5.5 inch phone. certainly easier to handle than my Galaxy Note 4 that I used to have, and the ASUS does have the nifty one-hand mode that shrinks the screen and moves it to the side, which is handy. I like the volume on the back as well. Power button is hard to press and hard to use on the top, but tap to wake/sleep works well so no biggie.
Performance - Flawless, in practice. Really fast. No stutters, pauses, crashes, redraws. Just gets it done, multitasking, games, whatever. zero complaints at all here. Screen has good brightness and resolution, sound quality is very good from headphones, adequate from speaker. No issues at all with heat, signal reception, voice quality, etc.
UI - I really REALLY like ZenUI, and a lot of the apps/features that come with it. Reminds me of HTC Sense in that there are a lot of logical improvements to Android, without feeling like unnecessary bloatware. Things like What's Next, Save for Later, and PC Link are genuine value adds.
Camera - been lots of discussion here. I've done a lot of testing, and here's the real deal. the camera defaults are terrible...the image optimization is a horrid mess that turns good pictures into impressionist paintings, and for some reason the default is also "standard" image quality, rather than "fine". I have no idea why that's even a choice, but there you go. Once you turn off image optimization, and change quality to Fine, the camera is really good. It does not have OIS, which is to be expected at this price point, but the dynamic range is adequate and the color balance is very good. With the image optimization completely off, resolved detail is extremely high, which is a good thing...but you will also see a bit more "noise", or grain, than you're used to seeing from other cameras that apply just a little noise reduction. The ASUS camera does give you the option to do that, I just have decided I'd rather go with a bit of noise and better resolved detail.
Video is quite another story. While the camera does do 1080p video, the quality is middling at best. Without OIS, there is quite a bit of shaking, and the image stabilization is mediocre. Also, the image stabilization only works for 720p video.
Battery - the battery situation is basically ok. Standby is fine...I lose less than 2% battery per hour during standby, and that's with an exchange account, an outlook account, and three Gmail accounts syncing at all times, along with high accuracy location and google now enabled. Screen-on battery is a bit higher than ideal...in regular use, expect about 4 hours, not much more. However, since the quick charger is...quick, I haven't found this to be a big problem.
My only frustration at the moment is that the phone is still on 5.0, rather than 5.0.2. That means smartlock is still busted for certain exchange accounts (like mine) that mandate at PIN code. This is a Google problem, not an ASUS problem.
Hope that helps...