I have played it to about level 13. I was very impressed to begin with, the art and mechanics are very good, much better than D3 and TL2. However the gameplay gets very stale, and its completely unplayable without relying on AOE attacks because there are SO MANY monsters.
Character customization and skill trees are very limited, theres only 9 main skills in each of the two trees (one is for ranged characters, the other for melee), and 3 of them are passives (for the melee tree at least, I didn't look at the ranged tree much). So theres 6 active skills for me to choose from, and half of them require mana and/or have their damage based off my spellpower. So basically as a melee character who doesn't want to be a spellcaster, I have my 3 skills already picked out for me. Not that I even need 3 because I can only have 2 active skills at a time.
Multiplayer is also completely broken. I've never managed to actually join a random persons multiplayer game, it just sits there trying to connect forever. I tried to play with 2 different friends who live in the same city as me and the lag is obnoxious and I get disconnected all the time. Theres also numerous bugs and broken quests (whether in single or multiplayer).
I'll probably finish it at some point but I've become bored with it already. I'm hopeful that it will become a much more complete game after the future episodes are released, but right now its quite disappointing. If they could just fix all the bugs and get multiplayer to work I would consider it worth $15, but I won't be buying the other episodes unless they add some considerable depth to the skill systems.