I love the new LFG tool in World of Warcraft. It's been a godsend and helped erased the memory of Blizzard's past failures to make grouping easier. The reworking of the daily dungeon quests plays a big role in it's popularity, but I like to think it adds a lot of functionality to the game besides just being an emblem farming tool. I'm sure we'll see the majority of players make use of it when leveling up new worgen/goblin characters in the next expansion. The only problem I have with the LFG tool is that the unbalanced queue times for DPS classes are causing some issues. I understand that Healing and Tanking are the less popular roles in the MMO trinity and I don't really have a problem with them finding groups faster.
I'm not that worried about this trend right now when most people are overly geared for heroics. However, it might start becoming a major issue in the expansion when player's can't just breeze through dungeons. I play a paladin and a shaman which thankfully means I have access to instant queue times. However, warlocks, rogues, mages, and hunters can only DPS and are really hurt by a dungeon group being broken up early. I'm not sure what Blizzard can do to fix the issue, but it's becoming obvious that these classes will gear up at a much slower rate. The only real way to avoid the problem is to queue up for dungeons with a friend who plays a tank or healer.