I have made several friends (that have translated into real life friendships) through WoW. WoW has also been a good way for me to stay in touch with friends and family that I knew in real life first but don't get to see very often otherwise due to time, distance, and other physical limitations. It's great to be able to play with those people and "see" them regularly.
None. Not everyone who plays WoW has some kind of severe addiction! There is a huge divide between the people who play casually, people who play seriously but within healthy perimeters, and the people who sacrifice critical life responsibilities for the game.
WoW indirectly led to my job (which I really like), some great friends, and a lot of really cool opportunities. I wouldn't say I'm a better (or worse) person for having played it, but I think it's been a generally positive influence on my life in the things that have resulted from it. I can't really think of any real negatives, aside from money lost, but I probably would have just spent that sub money on other games or hobbies anyway.
I may be an outlier in that sense, but I also strongly disagree on a general level that gaming in general is an unproductive waste of time, at least not anymore than any other personal hobby. In many ways, games are useful and have great potential to do good. I'm not the only one that feels that way.