I actually saw an article on Ars Technica abou this at first.
It's really impressive: The original game struggled to run full speed at points, but utilizing the boosted clock speed of the GBC's CPU eliminates all of that. The tradeoff is that this actually makes some of those parts harder since you don't get the typical FPS drop to assist in dodging shit.
Luigi's physics are... bizarre, though. Definitely taking some getting used to playing as him. Other than that, the palette choices and such are very nice.Good work.