Stability: Mostly minor glitches that can be ignored. The only exception being one time where the end boss froze and I had to restart the game. But that only happened once and I couldn't get it to happen again. So mostly stable. No lag or other performance issues- which of course makes sense, given that it's a fairly basic 2d game.
Content: Only a few levels, but each one is pretty well packed with obstacles and enemies. The difficulty can make it seem longer than it is.
Gameplay: Confusing and not the most intuitive. Even with the tutorial tips and the manual, some things just aren't obvious. It's a neat idea of having to essentially collect the enemies' attacks while your shield is up in order to fire them back, though. The game can be frustratingly difficult at times, and said difficulty can fluctuate a lot. Rather than being a curve, it's more like a roller coaster. For example, the end boss has several phases, of which the third is arguably ten times more difficult than all other stages, including the final, which was easier than the first two.
Aesthetics: Graphics are decent enough for what it is. The h-animations could stand to be a little faster and more dynamic- as it is, many of them are on the subdued side. The art style isn't particularly noteworthy in a positive OR negative manner. The music and sounds are equally unremarkable. All said, it's not especially pleasing to look at, but not bad either. The enemies mostly look the same, but they're cute enough that it's not too annoying.
XXX: Pretty vanilla for the most part, but a good bit of it, and varied enough within those limits. 17 enemies (plus the two MCs), several of which have alternate animations, as well as a nice bootyful game over screen which changes based on the outfit you're wearing at the time. Not amazing h-content overall, but nice enough.
Overall: Pretty middle-of-the-road. The biggest complaint I have is the difficulty, which is all over the place, and just plain (in my opinion) stupid at times. Otherwise it's decent enough, though. The characters are cute and the XXX content is nice, even if the animations could use some improvement.