Razer surveyed over 4,000 World of Warcraft players about how they play the game and what their primary motivations are. While it isn't exactly the greatest sample size, and is limited to people who are active in the Razer community, there is some interesting stats displayed in the accompanying infographic. Over half the respondents say they play more than 20 hours per week, and most have been playing for over 5 years. When forced to choose, 77% prefer PvE content over PvP, but if there was an option for "I participate in both aspects of the game" I think you would have seen a healthy percentage in that category as well.
Perhaps the most interesting statistics are the competition numbers. 80% of the respondents would like to see more competition between guilds, and 70% say they want to see more competitive raid tournaments. Do you think there's a place for more competition in the PvE realm? Challenge mode leaderboards are the only Blizzard-supported feature we have currently, and live raid competitions are few are far between (usually just BlizzCon). You can check out the full survey results over at Razer.