slow updates aint a big deal for me...it shouldn't be a factor for buying a Nexus 4 over Xperia ZR. Most changes are almost un-noticable. Sure psychologically it gives a positive vibe, but thats it. 4.2 biggest wow factor was Google now (meh).
4.3 wow factor is Bluetooth 4.0 support, OpenGLS 3.0 support and multi-user profile. All meh to me..Bluetooth and OpenGLS 3.0 is hardware dependent(although even the Adreno305 supports it) And how many games will actually be able to utilise it. Whether existing games based on Open GL 2.0 will benefit from it, i dont know.
The only thing that will make me want is it is the minor performance improvement, but one can easily live without this update.
After ICS, there hasnt been a single update that really made me WANT an update. Waiting on Android 5.0.