Many things to do; lots of fun to have. There are more pros then cons; everyone should try this game at least once.
PROS: There are games that just sit there and have you fight, and not get involved at all (coughcough Runescape). However, in Mabinogi the fighting system is quite advanced. You control your players attacks, making a truly innovative fighting system. This game has many skills to learn, so you will always be striving to make your character stronger, and better. Don't feel like fighting? No problem! In Mabinogi you don't need to fight to make cash. You can make goods and sell them to NPCs and other players, or perform part-time jobs where the rewards differ based on your performance. There is quite a lot to do, so you will often find yourself overwhelmed with everything! There are two continents (at the time of this review), one of which is massive! The world is sprawling and beautifully detailed. The party system allows you to join up with your friends to fight together! At least one event is usually occurring! The gameplay is free, with option to buy extra items with money, but this is not required.
CONS: The game is excellent, however there is difficulty with dungeons. It takes quite a while to work up the level to move on the next hardest dungeon so you may solo it without being beaten. Leveling takes a while once you reach higher levels. Lag is sometimes a serious problem at events. A choppy language translation sometimes makes the game hard to understand. As with all games, this game has its fair share of rude players.
Mabinogi is an excellent game, and everyone should try it at least once. Especially since it's free!