Everyone is gonna do what they are gonna do no matter what I say about WoW, and some (Enron) possibly because of what I say about WoW, but let me throw my 2 cents in coming from someone that was pretty heavy into the game about a year ago:
1) Enjoy the ride. If you don't enjoy your time playing as you work your way to 85, it ain't for you.
2) There is lots and lots of challenging content on the way to 85. Dungeons and Battlegrounds are terrific ways to level pretty efficiently and have fun PvPing as well as learning the boss fights in dungeons. The random dungeon tool is great for this.
3) Achievements are nothing to scoff at as far as a motivator for playing. MOST do nothing for you in game, a rare few offer kick-ass flying mounts and titles, but the challenge of completing them is definately interesting enough for me to keep trying them. Feel like a dungeon has nothing to offer you after the 10th time you have run it? Try it on heroic (if it's offered) and then try to do some of the associated achievements like timed-runs, or take down the boss with no one suffering from a certain attack, etc. Kept things fresh and fun for me.
4) Guild runs in ANYTHING is more fun. 5 man dungeon runs with only people you know that may or may not know the content is one of the best things going. Learning to tank/heal/etc. bosses and 'dungeon tricks' is a blast!
5) Run the addon "Recount". This lets you see your DPS (HOTs, total damage, etc.) and helps you to really dial in your attack cycles and keeps you on the hook for running dungeons that have items that you really need/want so you can take your dps to the next level.
6) Try getting on a 2v2 or 3v3 Arena team. If you think you are badass and the game is too easy for you, this will be a HELL OF A WAKEUP CALL! And another thing to work on, practice, and improve on.
7) Explore other characters for a while. Different classes will offer different challenges for the same quest.
8) I agree it can be easy at times, which isn't altogether bad for me as I simply enjoy the ride.
9) Getting into an active guild will change your perspective significantly as well. If you have mature guildies, a lot of new play options will open up.
In the end, I will never convince anyone to play (though I might push Enron and Rudy further away with my efforts), but if you are dissatisfied with what you are doing, try something else out and see if that is interesting.
I had a friend at work that only wanted to powerlevel because he thought the endgame and being the best/highest level/etc. was the only way to play. After he achieved badassness, he went back and took it slower, explored other characters, got into the fluff, etc. and has been enjoying the ride ever since.
Again, I'm just sayin'. :)