It's fair to say that there has never been a better time to be a warlock. Prior to MoP (excluding TBC and Classic to a lesser extent), warlocks were the least played class and were nothing notable in PvE, though they were sometimes good at PvP.
Now, I would daresay that warlocks are more popular than rogues, shamans, and the like (of course, my thought here could be wrong). There are three unique specializations, an extremely cool class quest, and DPS/utility/etc. has been at Flavor of the Month levels the entire expansion. There have certainly been some burrs here and there, but it's a great step forward from the days of Wrath of the Lich King and Cataclysm, is it not?