WoW is a adictive game if you want to be the best geared player you can possibly be. However it can also be fun to play a couple hours here or there. Like MMO's its much more fun when you have real life friends to play with. If you want to do instances (which is pretty much where you will get the best equipement/weapons) you need to play for 3 to 5 hours at a time. WoW does have a lot of fun quests you can solo, but once you get to level 60 you can either start pvp'ing or start doing end game dungeons, which can be a time consuming.
I played 4 or 5 nights a week raiding a few months ago, and had to step back and only raid a couple nights a week, which works much better for me. I recommend picking a RP-PVE server as they tend to have less leet speak kids, however it still occurs on all servers. Pick a PvP server if you want to compete with other players while you level. Also check the status. You want to pick one that is new, or low population, unless you have a server with friends on it already.