My only issue with fremium games is they can cost as much as full desktop or console games with no where the quality.
GLU's Heroes of Destiny is a prime example. The game is easy at first but you get a few levels into the game and realize they want you to spend hundreds of dollars on GLU coins to keep going otherwise the game becomes near impossible and no fun - the item drops are only for the characters one has to purchase so it almost forces you to pay a lot. I paid $4.99 for the customary 100 GLU coins and went through them quite quickly and realized the game is so badly skewed that I would have ended up paying more than Skyrim or Diablo 3 on launch day to continue playing a sh*t game...
I'd much rather pay up front a few dollars - usually less than a cup of coffee at Star Shmucks and enjoy a game - Example: Bard's Tale for Android - Amazing, hilarious, well written and a blast to play, worth every penny and it's currently $2.99 - compare that to the crap the GLU produces and no wonder people pirate those coins. GLU's game is a hack by comparison.
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!