Hey, thanks for the crit Psychedelic Eyeball! Sorry if my previous post came across sounding very ... um, needy. That was kinda uncool of me.
If I may address the negatives you mentioned (keeping in mind that I understand that it was the result of poor direction on my part if you didn't get what I was going for, or that I just plain screwed up). Also, I welcome any and all constructive criticism since it helps us grow and get better, so don't ever get the wrong impression and think I'm trying to be defensive or dismissive.
1) Sandy Mountain, it's a speed-run level 100% and maybe it wasn't the best idea to put it into the chapter since it's the only one of it's kind. I envisioned once it was up in the portal that people might want to compare top times on it, that's really the appeal on that one.
2) Ice Truck Killer was sort of a gestalt for me... I realized one night that I don't think I'd ever seen anyone try to make a level with invisible blocks, then I also thought, "how cool is it that meat boy leaves blood smears on the edges of all surfaces, even the invisible ones...". Then I remembered that when he spatters in a saw, bits of blood land on surfaces below him.
The thought behind this level was that you'd have to suicide a number of times to reveal the path of invisible blocks, then hop to the finish. I tried to imply what was you were to do by offering an easily reachable blade with no obvious path up hoping you'd hit it accidentally or intentionally and realize what the deal was. Honestly, I may have been blinded by my perception of a fresh idea and missed the possibility that it may be too far from the traditional gameplay we all signed on to experience in SMB.
3) Floater: I guess I can't really argue your point on that. The only thing I have to say is that I found the gravity wells pretty easy to hop around in personally, but for everyone else, it may have been more frustrating than it was worth. After testing it for about 15 or so minutes I was able to zoom right up them several times in a row, but not consistently. I thought it would be something different.
4) Salt, Injury, Madness: Hmm, I was able to get up the final jump just off the highest exposed edge before the salt started. I actually moved the salt even higher just before publishing it. Sorry if it was annoying. It is a really tight jump though for sure.
Finally, I totally hear you on the weird jumps in Gentle Rain, I just didn't have the heart to get rid of the inclines, and the glitch jump you mentioned I thought kinda pushed the player past the conventional jumping mechanics in the normal game, so I thought it would be appropriate.
Every level is definitely beatable, I've done them all many times now, although, I have had an unfair amount of practice.
Thanks to everyone who tried the chapter out, I really appreciate it. Everybody has been very generous with praise on most of my work and I couldn't ask for anything more than that.