I played for about 9 months. At first it was incredible -- I played day and night sometimes on weekends and holidays. It was very addictive. I worked my way to the top then started raiding with a guild. All was great, and I made a few friends.
The pros were: the graphics, beauty, creativeness, and fluidity.
*Boss fights have to be carefully orchestrated.
*PvP between equally matched (and closely geared) players is a ton of fun. Especially when you go toe-to-toe with someone playing the same class as you.
A few months later, my best friend I made in the game left because another person in my guild didn't like her and she moved her character to another server. I had other friends in the game, but our play schedules were incompatible. So, I rarely saw them. I continued playing for a few months, but lost all interest in what had become a grind.
I made about 6 characters, and frequented different servers, but with so many people, I rarely played with the same person twice.
The biggest flaw: Essentially, you have a Multiplayer game with no community unless you join a guild and play enough to get on raids. They're very competitive and there's a pecking order. It's a bit like a job at hat level: you have to show up for raids regularly, and establish your worth to get in on popular guild raids. If you have a loser guild, then you lack the fun of playing with friends. So it's an all or nothing thing, usually.
So, with no sense of community, the game's flaws started getting more annoying.
*your combat was just pushing sequences on button at the right time and watching meters refill.
*The skills required to play are very low the more powerful you get, or with certain classes. So, the game gets less interesting. There's a running joke about people "rolling their face across the keyboard and getting a kill."
*Boss fights (while carefully planned) become a boring routine. And if one person messes up in the fight, the entire party can wipe. Meaning a long run back to the body from the closest graveyard.
*You're on a gear treadmill. The best equipment is a grind to get, and some very rare items are like slot machine jackpots, which is frustrating.
*Without the best gear, you're a sitting duck in PVP.
*Too many of the same type of quests: "kill X number of creatures." or "collect X number of this item dropped by dead creatures at random intervals." some are "run here, talk to this person, then run there talk to another person... etc." and some are "escort this NPC along this route." Blizz addressed this by making more types of quests, but also made things easier, not necessarily more interesting.
*When there is an expansion the level cap rises, and all the gear you worked so hard to get becomes worthless.
*Nothing you do can permanently change the world. Kill the boss at the end of a dungeon and he'll be back for you and others to kill later.
*There are a ton of servers, meaning the player base is fractured. So, even if you find a friend that plays, you'll either have to start a new character on the same server as them (or vice versa) or play an expensive transfer fee.
*It's around $80 for 6 months of play at the best rate.
All in all, WoW is the best 3D MMORPG out there. But it can only hold your attention for so long, because while there's a ton of equipment, a vast world and some interesting storylines. It lacks community, permanent one time world altering events players can take place in, and a combat system that consists of just pushing a button and waiting to push the next one -- so no real skill is needed (except PvP with tactically talented players).