I got to the fourth round but I was getting frustrated with the gameplay. I like the RPG element though. The character screen and the story presentation reminded me a bit of Diablo.
You have to replay levels a bunch to make enough money, but I don't mind because some levels are really pretty fun (I like the beach ones).
The thing that I find so addicting is the arrow-shooting. Once you get very accurate you can pull off some pretty crazy shots (my favorite is getting a headshot while just barely shooting around one of your allied guys).