Ok i seen a lot of complaints about this game... I even complained about this game myself at one point. This comparision will be to help compare to some REAL grinder games. Compare it to Flyff... I played flyff for over a year, and had a character at around lvl 32 (not bad right) even pushing that more so killing one monster took about 2 - 3 seconds with a REALLY fast merc. each monster gave about .01% (not good). and 80 quests over roughly 160 levels... thats one every 2 levels...
Compared to maplestory... ok my highest character in maplestory is about 46 which isn't bad... one party quest run gets me about 10% which takes about a half hour. Even with grinding I can two hit kill a monster for about .02 to .03 per kill. roughly into the thousands when it comes to quests...
The two only big beefs I have about this game is getting from level 15 to 20, which is the most difficult part of the game. Once you hit 20 the game seems to take off at an incredibly fast rate. Doing Party quests with a few hours you can easily get 3+ levels a day (2 or 3 hours play). Secondly the prices on items in this game are OVERPRICED! Sauna robes sell for 2 million mesos easily, 10% dex scrolls sell for 500k easily. Weird classes are overrated today, such as dexless... They are fantastic up until 70 then they are entirely useless and weak compared to everything else.
My suggestion to new players is to research into classes before you start (look up maplestory strategy wiki) < that will inform you on EVERYTHING. Also be prepared for the grind from 15 to 20 it is harsh.

I, too, have complained about this game. I made it to level 28 with my mage and its taking forever to get to level 30, the class upgrade level. I just gave up on it. I went back to it again later to see if i could get there but i encountered the same problem and just left again.

I too complained about the game, it takes too long to level up.  I found after a while that it's better to explore and to chat then just try to level up.  Me and my friend got to level 132 and then a guy (i'm not sure his name) hacked us and stole everything we had.  I decided to put a report in but that achieved nothing.  I just quit the game and never played since.

 Leveling fast in this game is a piece of cake, as long as you know all of the training spots you can get to level 30 without founding/double exp in a matter of days, 4-5 days is easy obtainable, I did myself get 1-30 on 2 days playtime with double exp. You can always just ask higher level people, most of the people playing Maplestory are very kind persons which gladly helps, just try to stay away from the other ones.