You can do free trials all you want, but none of them reflect even a fraction of what gameplay is like at the level cap. I've been playing WoW since 2005, I played 3+ years of LineageII, (No, I am not Korean)I played WH:O for several months after release...
Let me give you a couple tips to help you avoid wasting MASSIVE amounts of time:
1. MMO's are for people who want to play the same game for years on end. The best players in WoW are the ones who are established and regular. If you want to play a game sparsely or only when your busy life/work schedule permits, I would highly advise steering clear of MMO's. Why? because you will be average. Forever.
2. In my firm and experienced opinion, the grind to the level cap is the mediocre part that everyone *gets through*. It is a destination, not a journey. You will not enjoy it in WoW if you are on a PvP server, that is for damn sure. (LoL bored level 80's)
3. Finally, I stress the point that you should not try an MMO if you are not truly seeking a never-ending game. Thats what they are.
Oh, and enjoy things like expansions coming out, dropping you back to a level playing field with everyone else, only to have to work back up to the top of the food chain.
If these things don't interest you, Stop now.
If they do, Welcome to the world of MMO's.
P.s. (heavy WoW slant on my opinions.. with a touch of LineageII)