I don't like it because it feels sloppy, it is very limited, and it makes me phase way too much, it gets really annoying.
Plus, it makes your server choice obsolete. I wanted to play on a horde-dominated server, and it cata that is just what I got... but in MoP all the sudden there are alliance all over durotar ganking people.
And as if the community wasn't bad enough, CRZ came in and executed whatever community was still left.
ALSO- I play on a "full" server, so why the hell am I being paired with over 5 goddamn servers?!
And don't even try to pull the "just play a single player game" card because i'm pretty sure WoW was still an MMO Vanilla-Cata