I'd like to ask a question. For someone like me who has always played single player RPGs like Oblivion or Skyrim or Might and Magic or Wizardry etc., what is it like to find yourself in one of these massively multiplayer online RPGs like WoW? Do you adventure by yourself? Do you always adventure with other players? How do you find them? When you start out do you feel helpless? What's it like?
Typically speaking, the lure to MMORPGs is the amount of progression, content, replayability, and challenge in the games. Unlike Single Player games, they last a heck of a lot longer. Many MMORPGs soloing is perfectly viable method of leveling, but provides limited opportunities "high-end" or at level cap. In almost all MMORPGs you are going to have to socialize and play in a group. The biggest downside to MMORPGs is the fact that you cannot just "stop" whenever you want because you are working in a group with others. Many tasks take a long time to complete. How you are rewarded "loot" is sometimes tricky as well. You may not always receieve a reward it depends on how the loot is structured. This is much better than the past. Depending on the class you pick, yes some classes solo much better than others. Some simply cannot solo. In Player v Player cases, this is sometimes especially true.
If you are in grade school or college, I would suggest trying out MMORPGs. They are incredibly fun, but extremely demanding. It is fairly rare to have a "casual" friendly MMORPG. People say WoW is, and to some extent that is true - however if you want "the best" items and to progress, you have to Raid and invest yourself in strong social aspect of the game. Finding a GOOD guild is half the battle of an MMORPG. Once you find the right fit for you, typically you guys can move from game to game with ease and it makes the experience much more enjoyable.
I would say however, no MMORPG today is very good. Wait until Guild Wars 2 if I were you.