i've played DayZ, and found it engaging, but of course with the ARMA2 UI...clunky. i've been trying to gather as much information on The War Z as i can, and i am tempted to have a go with one of the pre-release packages. it seems more streamlined and user-friendly. of course i know Dean "Rocket" Hall has big plans for the stand-alone DayZ, so we'll see what he can do to improve the user-experience as far as patches, compatibility and all the nonsense that makes DayZ a challenge to play casually. regardless, here's some more info on The War Z...which looks quite promising
GDC Online 2012: A (severed) hands-on with The War Z | Massively