What I really liked was the progression of the game and the levels. Most levels can be completed quickly and if you try to take your time, you're met with an particularly nasty baddy who chases you around. So while there are a ton of levels to play through, you get a consistent sense of satisfaction upon completing each one. I also noted the difficulty curve which seemed just right and the balance of risk/reward to collect all of the points (which are fruit for some reason) that grant valuable extra lives. Since you get killed with just one hit, sometimes you really have to weigh the cost/time required to grab those higher-point items.
I also found the enemy types to be nicely varied. Again, they aren't much to look at, but their attack methods need to be learned and anticipated especially when they start mixing enemy types. As you progress, you'll find tougher variations on the same enemy types and some bosses sprinkled in (see screenshot) for good measure.
What initially bothered me was the controls, namely the jumping which I found to be odd and very "floaty." In my early going, it created some frustration and questionable deaths - and while I was able to adjust, I would have liked to work with more responsive and tight jumps. Considering that some later levels are absolutely packed with enemies, the need for agility is high.
But Nasty makes up for these things shortcomings with a strong vision of overall play experience. Mashing your way though 100+ levels by yourself or with a friend is undeniably a good time - you don't get much in the way of flashy or gory action like "Gam3" or "Veks and Silence" but you get a challenging, more platformer-based experience that will have you saying "just one more level, then I go to bed - okay just one more."
At 400MP, it's unfortunate that Nasty will seem higher-priced. Based on the graphics and first impression, that may create an initial barrier to sales. While I feel the game deserves the 400MP based on the sheer number of levels, it might do better to reduce to 240MP at the first opportunity. Happy shooting.