In other words, DSO is based on grinding. That's frequently the case with action RPGs, but unfortunately DSO doesn't have enough variety and so the grinding feels like grinding. Whatever level your character is, there are always roughly two maps where you can find enemies of a reasonable difficulty, but the maps aren't very big, and you'll probably get tired of fighting the creatures in your map well before you can move on to the next.
There are about 40 maps in the DSO world, including the newish islands of Atlantis. Some of these maps are open connector zones, where you can run into other people, and others are dungeons, which are instanced to you and your party. If you reach the maximum level of 40, then you can also explore some "parallel worlds," which are more dangerous versions of the lower level maps. I didn't make it to level 40 (my interest waned early, and I only reached level 18), but it seems like sort of a cheap strategy to re-use maps rather than create new ones.
While you're grinding your way through the game, you'll of course find lots of equipment. Items come in a variety of tiers, from normal (white) to improved (green) to magic (blue) to extraordinary (purple) and finally to legendary (orange). I found some extraordinary items while I was playing, but no legendary items. Some items have slots in them that you can fill with gems, and there are also some set items. That is, DSO has all of the equipment bells and whistles that you'd expect from an action RPG.
Some of the more interesting items you can pick up are essences. Essences give nice bonuses to your damage (up to a 300% increase), but they're used up every time you attack, and so they're best saved for tough battles. There are also work benches you can use to create equipment. If you place four unidentified items of the same type on a work bench, then you'll get back an unidentified item from the next tier up, which is a nice way to reward people who are patient (and who have lots of storage space). Finally, you can also make small upgrades to your equipment by paying blacksmiths and armorers
While DSO is listed as free-to-play, that's a bit misleading. The standard currency in the game (gold, silver, bronze) buys you almost nothing. All of the good stuff costs "andermant," which you can purchase using real money. Quests typically reward you with andermant, and you can also find some when killing enemies, but these are minor sources. I only collected 1200 andermant by level 18 (and that was mostly due to starting out with 600). Meanwhile, increasing your inventory size from 21 slots (which is barely big enough for quest items and the things you have to carry) to 28 slots costs 1600 andermant, and identifying a single extraordinary item costs about 400 andermant.
Free-to-play games always have a difficult line to walk. They have to be fun enough to play for free, but better if you pay real money. In DSO, I always felt like I had to protect my wallet more than my character. I couldn't even afford to identify the equipment that I found, let alone buy anything interesting. I suspect that playing DSO to level 40 will cost you more than playing Torchlight II ($20) and perhaps more than even Diablo III ($60), all while offering inferior content. For me, a free-to-play game has to prove that it's worthwhile before I spend any money on it, and DSO didn't even come close to meeting that standard.
Overall, Drakensang Online (DSO) underwhelmed me. The action RPG elements are basic, the MMO elements are basic, and even combining them (which I hadn't seen before) wasn't enough to draw my interest. The game is certainly playable, but between the grinding combat and the nickel and diming costs, I just don't understand how people can spend a long time with it. Originally, I had planned to play DSO until at least level 20, but in the end I just couldn't force myself to do it, and I gave up at level 18.
All that being said, DSO is free-to-play (at least technically), it doesn't have any noticeable bugs or lag issues, and it works in 10-30 minute chunks, which is typically what I look for in a browser game. Plus, the game doesn't require any sort of download, and so you can try it out with the most minimal of investments. Just don't expect anything spectacular when you play.