I thought this game was pretty fun actually. I think people who are upset about it are misunderstanding some of the game mechanics.
First, to people saying that upgrading EXP is a bad thing: Leveling up IS helpful. It increases your max HP (until you die) and when you level up, everyone on the screen blows up, not to mention your HP is refilled. Couple this with the fact that it has a sort of Earthbound style HP gauge - that is to say, even if you take enough damage to kill you, your health bar slowly slides down to 0 before you actually do) you can actually use the +% EXP gained upgrade to tank pretty effectively and make money.
As to people complaining about how hard it is to make money, please note that when you die, you keep all the money you made in that unsuccessful run. In fact, there's even an upgrade button in the bottom right corner on the "try again" screen so you can upgrade in between failed runs. So, money gained never outpaced how much money I needed. I could usually upgrade every run, and always every two runs. I'd say I died at most 3 times in any level. Furthermore dubesor complains about the 4k cost to max out any stats, to which I reply that I didn't max out any in order to beat the game. In fact my HP upgrade only costs 2k at this point. I'm not saying this to pick on anybody, I'm just trying to point out that this game isn't all about stats. It's about dodging reflexes, strategy (do I try to level up, time when I level up to take out more guys, or just play defensively for now?), and gambling (should I attack that enemy? I may die, or I may level up!).
I thought the difficulty curve was perfect, as more and more complicating elements were introduced with each successive level. I enjoyed the risk/reward elements. The graphics were cute. Music and sound was spot on. The whole retro-ish thing was successful. Kudos!