I played it for about 2 years total. I took a break of about 4 months a few months after it opened, came back through Burning Crusade, got to 70 and called it quits.
Stormreaver/Horde
As an old school EQ player, I think WoW ruined the genre, generally. The old MMO community that existed from UO, EQ, and then DAOC was inundated by 10 million new players, the VAST majority of whom were immature or short attention span theater. Don't get me wrong, the old MMO community was primarily some of the meanest, greediest people around, but to a large extent, they were also more mature (relative...) and, by far, they were easier to have a discussion with.
I have to say that a couple things about WoW I absolutely hated. The first was the "go fetch" quest system that it really brought into it's own. Old school quests were a lot more obnoxious, longer, required more camping and were generally goofy, but I at least felt like I was free to camp, explore, or just do whatever I chose. WoW created a grindfest that truly felt like a treadmill of completing quests in x zone, then quests in y zone in order to level. It absolutely REQUIRED this sort of gameplay in Burning Crusade.
It's funny that most games now claim that they have done away with this style of quest system. Bioware in particular claims that it no longer exists in The Old Republic. We'll see.
It was my fault for agreeing with my guild to go to a PVP server, which was a complete idiot-fest, so I won't bring that up. That's not the game's fault.
I hate the loot/gear system in WoW. One of things I really liked about EQ was that gear initially was VERY rare and VERY valuable. It was also pretty distinctive, even if it was just a palette swap. People looked absurdly colorblind due to the mishmash of colors they wore, but you wore what was good, you wore what you got, and you mixed to get the stats you want. For the most part, everyone in WoW looks the same for each class as they raid to get the same damned gear.
I hate the fact that WoW's dungeon and raid encounters are not really skill based so much as gimmick based. In EQ, it was a matter of getting a large number of people to simply play their class well in a raid encounter. "This is your job, don't screw it up." Bosses were easier from a strategy standpoint in EQ, but things went wrong a lot faster. One bad aggro from a rogue could end an encounter. In WoW, it's more about 10 people inserting tab A into slot B at 41 seconds, and then another 10 people running 50 feet to their left at 50 seconds and then all standing still for the next 30 seconds. It's realy just a matter of getting 24-40 goobers to all follow the same script correctly, which simply isn't fun to lead... or to follow for that matter. Killing in WoW felt more like "wow, I'm glad we're done that encounter" rather than the "zomg we killed it" rush that I often got in EQ.
There is no FEAR in WoW. I presume UO had fear due to the harsh PK penalties. I know EQ had fear due to the harsh corpse recovery. Yes, late night CR's sucked the ass. They also made you respect the encounter and dungeons a hell of a lot more.
And WoW made one absolute cardinal, mortal, they should all die in a fire sin: they pressed the reset button on raid progression with Burning Crusade. All the work you did and all the accomplishment you got from clearing Molten Core, Blackwing Lair, Ahn'Qiraj, Naxxramas just got shot to hell by getting your first piece of green piece of armor that is better than that epic drop you were wearing after weeks of clearing raid dungeons. That's just called kicking your raid-centric players in the teeth. It's ok to create regular casual/dungeon drops that are better than raid gear from a couple years/expansions back, but not from stuff you just implemented in the game less than a year before.
Anyway, WoW had promise. It obviously appeals to a lot of people still. That's all well and good. I enjoyed the old days a lot more. I'm looking forward to seeing if The Old Republic can bridge the gap of rewarding both casual players and hardcore players without crapping all over one or the other, or both.