Some of these levels... it seems like there was an extensive lack of playtesting - on 44, especially, I got through more because of luck than anything else. Also, it seems there's a memory leak somewhere that causes the higher levels to load rather slowly when playing the game straight through.
Yes, Guitar Hero is better.
Yes, rhythm games should (almost always) be left to consoles and *gasp* Real Life.
Yes, lag makes it nigh-impossible to get all of the "perfect" awards.
Yes, this game roXXorz anyway. :D
In short? Replace "q is for 'quit the game'" with "q is for 'adjust visual quality'" and add more autoturret/missile/pulse RoF and damage/density boosts, and you've got a winner.
I'd like this game far more if the "countermeasure" was more effective at breaking off sections of the wall, if only to make "impossible" situations easier to get out of without losing a life or two.
My one complaint is that the level 2/purple projectile is better in every stat than the level 1/blue one -- higher stability, damage, and velocity, but it (somehow) also has lower energy consumption. So once you have the purple one, you'll never go back to using the blue -- unless you forget to specifically switch to purple after an antimatter powerup runs out. >_<
Going off of what Kail_Panille said, some of the later levels are also essentially impossible if you get a good start and then the computer tosses out five of the dashed circles (or the ones with the "_<
I do like how as you move through the game there's variations on how the cannon fires, and how there's a new powerup introduced every so often even once you hit the mid-60's.
 "Sola Rola - The Gravity Maze"){kind=icon}
 "Super Crazy Guitar Maniac Deluxe 2"){kind=icon}
 "- Shape Invasion -"){kind=icon}
 "Breach"){kind=icon}
 "Gamma Bros"){kind=tracking}
 "Momentum Missile Mayhem 2"){kind=icon}
 "Areas"){kind=icon}