I've played Dungeon Hunter 4 for about a month now after reading this article. It is a fun game, but once you run thru your gems (which doesn't take long w/ your first char because you probably don't realize how important they are and, soon enough, you learn how expensive they are) the game becomes a long drawn out grind.
I actually only get to play it maybe 30-40 mins a day.. the remainder of the day is devoted to waiting while charms are extracted from equipment or combined to become powerful. You can speed the process, but it cost gems. Everything really good costs gems... a lot of gems.
If I'd paid for and used gems to speed up the game so that I would be able to play more than 30-40 mins a day.. I would have spent $30+ just this month!! The devs SUPPOSEDLY offer sign up deals where you can get free gems for performing some action: downloading and playing other advertised games; signing up with some service or website; buying some product from one of their advertisers.. etc..
I completed several of these deals and have received NONE OF THE GEMS PROMISED. Emails to the devs about this generate an automatic reply.. but its' been weeks and still I haven't received the gems promised --- COMPLETE SCAM!
Fun game, but not worth that kinda of money.