So, after pretty much watching all the reviews on the entire planet, a few common complaints I see and (my own personal takeaways):
1. Buzzy/noisy 4 popper turbo and possible reliability issues.
(Well, this is the world with live in with all these crazy emissions standards, I do not think Lexus can do any other way. If the 4 cylinder is too noisy, just go with the hybrid.)
2. E-latches/doors (haven't tried them personally but people are not particularly fond of them)
3. New Steering Control + HUD setup (maybe they can always go back to good old layout with many physical buttons if all their customers are not happy with it)
4. Overly Aggressive/ Constant beeping safety systems ( This one also easy fix - just put a button to not beep at all and keep the alerts only the screens)
5. Screen way too big, eyesore especially during night time. ( People literally asked for bigger screens so deal with it )
All these things, like Mike said, wouldn't be just limited to the RX but also applies to the NX with same setup. Most of these 'problems' are easily fixable through software. People will always complain no matter what they do but overall I think they pretty much done a good job with this new model.