that's right, not much new thing going on, just stay with the last stable build. lazy to try new kernel 
opss.... that's pain.
if only screen issue, you should still able to backup data.
I touch both S4 and One demo unit before; no doubt, HTC One material build quality is really superb !

as long as there is developer for it... it surely can have that so called "nexus experience"

oh yeah.... HTC One Google Edition is official. just backup all your personal data, TB all user apps; all these to restore to other phone should be no problem, just remember don't backup/restore system apps will do.
coz both S4 and One have IR hardware, Android 4.3 will have IR native support 

Pain... No casing? 

Or you memang prepared to change phone 
Shouldn't be a problem to restore. But if you're going to 1080p models, some apps might have a different version for it to fit in that much pixels for better appearance. *I think so... *
Those Google editions all have different hardware from our Local version.

Ya... Don't restore system apps but I think is fine to restore things like Settings Storage (android ID) and other data (those normally in Green/Yellow colour in TiBa)
Nexus 4 is good in performance. No doubt for that. But things like camera is still sub-par just like Galaxy Nexus (interestingly find out that Nexus 4 macro is not as near as Galaxy Nexus just today, also find out that Nexus 4 lens is wider than Galaxy Nexus one). Nexus 4 display didn't syok me (maybe I'm used to vibrant colour on GNex). It's also not up to competition when compared to those newer models you mentioned.

But... Nexus 4 main advantage is price. AP set at 1.2k, Ori set at 1.3k+-. You will probably never get One/S4 at this price within next half year to 8 months.

It still depends on how deep your pocket is