I will take this opportunity to shamelessly self-advertise my videos of this game:
Lower Hub:
http://www.youtube.com/watch?v=Jl-V_7dvQXgRight Hub:
http://www.youtube.com/watch?v=88rD5iTRwTEUpper Path:
http://www.youtube.com/watch?v=JGWatE5awvwBefore JMan releases the new build with the new area and stuff, I'll post an update video showing the things that have been changed to keep my run up to date. This will include the slightly tougher Hubert and the fixed segment in the right hub. What else did you change? You said there were a couple other minor things.
Edit:
OK, I checked the game and the only other difference I could find was you fixing Anon's skip in NG3, which doesn't affect my run since I didn't use it.
Anyway, I was looking at the way you enter the new area in the hub you're building, where you split the right wall into two metal bars, the bottom of which is fake and the top is still real. I think you should switch that around, for if its the top part of the wall that's fake, you can only reach it by making use of both rightward moving blocks from the previous screen, effectively jumping over the spike wall with no further help (as I demonstrate in my Right Hub video). As it is, you only need the bottom of the two blocks, and then you rely on the platforms you added to finish jumping over the spike wall. I think that makes it feel more arbitrary and less reliant on the structure of the level.