Yes I wished I had stopped playing years before I actually wound up leaving. I think as a general rule most people don't super regret the time put into it and I don't either, what I regret is that I convinced myself those people in my guild and in vent were my friends.
I don't mean that in a "THEY HURT MY FEELINGS" way either. I mean that these people whom you spend all this time with and form very real connections with are not and usually will never actually be your friends. You talk to them every day and they wind up filling a social role that everybody needs but they are not your friends.
In a hardcore raiding guild skill is supposed to be the only thing that matters...well skill and time that is, unfortunately this is almost never true. Lying, backstabbing, manipulation and stupid power struggles are the real important things. I know it sounds incredibly stupid and petty but pushing content in a high end raiding guild is usually about ego anyway Those other things just come with the territory. I watched people who were the best of friends when both of them were online, become incredibly hateful and vicious when the other was not around. The shit talk, the gossip and bullshit was astounding.
Not to mention, if somehow, some poor girl stumbled into the guild, they would ratchet the backstabbing up a few notches. Giant dick measuring contests mixed with insane amounts of whoring their dps and achievements. All the while pretending to be nice and friendly with each other.
A friend once told me, you don't spend that much time on internet becoming that good at a game and not have something wrong with you. He was right, we were all socially dysfunctional psychopaths who managed to keep it together so we could raid and stroke our own egos. I didn't want to be that and walked. I made a lot of good memories despite all the bullshit and did manage to have quite the ride getting there, but once I realized that no one REALLY gave a shit about anyone else I wanted out and I regret I convinced myself for so long that it was ok.