The 360 and PC version were released on the 12. Was the PS3 version delayed? That's strange...
Having played through hard mode, the controls are tight and the game's fun, especially the shoot-em-up stages. Overall though it was easy. I didn't have much trouble with the stages or bosses, and the game gives you a lot of extra lives that it doesn't really matter. After you beat hard mode and fulfill the 'secret damage' requirements, you can play Gold Sparkster mode where the difficulty is similar to hard mode and you get only 4 hearts maximum. It's nowhere near the original Rocket Knight Adventures' Crazy Hard but should be a good challenge.
I was surprised at the inclusion of a scoring system! It's a basic timed chaining mechanic, similar to those in some shmups; after you kill an enemy or collect an item, you will add to a bonus multiplier. Killing another enemy or grabbing another item will give you the multiplied points and add to the multiplier again. But if you don't get an item/kill before time runs out, the multiplier bonus disappears and you have to start from the beginning.
The sounds like a remix of RKA's first stage theme. This is a nice touch!