Adam, I'm not sure you even played all of your levels before releasing your set. Actually, I'm sure you haven't, because Level 25 doesn't have any trapdoors... But here's my review of some of the levels (except some remakes and a couple that I didn't play.)
Other comments:
Level 3: Why do you need the hidden exit? I managed to save them both in the visible exit.
Level 4: What style does this use? (I don't think I have it.)
Levels 5 and 19: Hint, please!? I can't imagine how you can do that with only 2 diggers, but maybe I'm missing something... Also: They're not "very symmetrical". Look at the center of level 5, they're not even. And the window placement in both levels is off (not the same on both sides).
Level 6: This one was kind of fun.
Level 7: I still think this one is too easy, maybe you should give fewer builders...
Level 8: Stuck on this one... It doesn't seem like you have enough builders, but... A0;I'll have to try again...
Level 10: This one went from literally impossible (old version) to way too easy!
Level 11: You could have made this harder by having a tighter time limit...
Level 14: Probably my favorite of the set, but you give too many tools for it to be difficult.
Level 15: The time limit is very tight... I'll have to think about this one some more.
Level 20:
It seems like you have either not enough builders or not enough bashers. Tricky...
Level 25: No trapdoor = no lemmings = not possible!
Level 26: Why do you only require 59/60 and give two extra builders if the point is supposed to be perfection? (I have a slight idea about the extra builders, but not the 59/60...)
Level 27: Why is this even here? Seriously... At least Fun 5 was fun to play...
Level 30: Sorry, I don't have the patience right now
Now off to try Insane Steve's sets...