Well it's an official update from Google so it is stable. I have the nexus 7 2012 version and kitkat is incredibly smooth. Multitasking is very fast especially when switching apps. As far as software problem goes, none.
Whichever version of the nexus 7 you buy whether the 2012 or the 2013, you will better performance on the 2013 version as it has better hardware and more ram. You will definitely benefit from the millions of apps on the play store.