I honestly looked at it and thought, "Hey, this isn't gonna be that bad!" After playing it, that changed to, "It's not Hell Mode... it's Lead Poisoning Mode."
While hilarious and challenging, my only complaint is that some levels become impossible as certain characters due to unavoidable rings, such as on a spring at the end of Techno Hill 1 as Sonic. But, other than that, I'd be interested in seeing someone beat the game like this!