My takes on the X's key features...
The notch
I myself could get used to that. Getting an extra line's worth of space could be nice, and doing away with the network name as well (since in the US, roaming is a thing of the past). However, I could see that being a concern if you travel internationally and want to know what network you're on there. I could legitimately see other people preferring the traditional horizontal bar. It would be neat if there were an option to put that in for those that want more stuff displayed at a glance (although I doubt it).
No physical home button
IIRC, you swipe up to reveal the Control Center that also contains the Virtual Home button? I do like on my LG G4, swiping from up reveals the Android Notification bar, whereas swiping from down reveals the Home Touch buttons. Plus, I can go into the phone's settings and individually customize which apps I want this to be hidden, and which to be always on.
Looks neat, but I'm curious, not excited. And with ANY phone, if it costs more than $300, then I'll check it out when it drops below that price.