I tried this game and even if it is at its infant stage, it has already annoying things. These things are as follow.
1- They have a weight limit that you can carry in your inventory. NOT popular at all with players.
2- Not only you use MP for your skills, you also use SP. The SP is not available like MP potions. You have to kill mobs to get it up, but the down side is that if you use skills it won't go up that much. You need to kill them without skills to bring it up. It is also used to by skills and it should be limited to that purpose or anything that it is not related to skills.
Also, you are only allowed 1 char free for this game. If you want others you have to pay like $3 or $4 which I think is a crime.
For the rest it is pretty good and I love the idea of the Seal Tower where there is NPC that offers you quests. As you lvl you will get more and more of them and you can repeat them. They tell you what is the mininum of players needed and also the maximum for each one of these quests.
I will stop playing it and come back in a few month to see if they decide to get rid of SP for skill spamming and the weight limit for inventory.
I hope this help a bit