Actually what surprised me about the first 3 levels of the pack(I haven't played anything farther at the moment) was that if they were linear, it was very hard to tell. I just kept thinking When I finish playing the pack I shall write a review.
My list of Changes so far are-
Not so many carrots, while sometimes I wish I had one, more health makes me reckless and I just lose the heart anyways. But that's just me.
The first tile bugs I really noticed were in the Hell level, theres one near the beggining going up the slope(an extra tile was placed, doesn't ruin the gameplay but it just looks odd) and I found it odd that I got hurt just touching some normal looking ground.
I think thats it, oh, and if the levels were linear(as I said I couldn't tell), if you made them unlinear that would rock, but thats only if you want to make them unlinear if they were linear.