Experiences vary, for instance, I can pretty much say it has hurt the community.
As for LFD, well, in WoW, it would be a common sight to see someone who isn't a tank, join someone's group, and then that person queue as tank just so the other group member(s) get thrown into groups instantly, then the tank leaves.
Other common things include people needing items they don't need then leaving group (a lot worse on cross-realm), people (most notably tanks or healers) pulling monsters and leaving group, leaving the remaining members to die, and the general "I expect everyone in the group to know everything about everything" people.
Because of all above, I don't want LFD, unless action will be taken against people who take part in the above and other negative actions (I wouldn't be sad if those people were perma-banned, but I can see that as being a bit much ). I personally am doing just fine without LFD (I'm level 32 atm) and don't foresee any issues in the future that would be solved solely with LFD.