I'll have to play this soon, as I played the older demo.
Viewing post in Sweet-Tooth Stronghold: Another Test Stage Challenge comments
Only 2 complaints.
Speed. It's so hard to get to atleast Mach 3 (which even if you're only supposed to get it sparingly, atleast give it some sound effects so you can atleast feel like you're going fast.)
And losing your Mach when you hit an enemy (i believe its only if you're in 3 not 4) and bumping into enemies on mach whatever 1 2 hybrid.
Other than that thats my only gripes. Good so far.