I heard about the challenge on another fitness forum and started it about a month ago. When I took the initial test I could only do 2 push ups on my toes. I'm up to 46 now!
I was inspired by Cathe's PERFECT push ups in the STS clips to do this challenge. I've been doing them on my knees for years and that strategy has never prepared me for doing them on my toes. Right now I'm ONLY doing them on my toes and I refuse to drop to my knees.
I actually went back to week one and restarted the challenge using the levels in the second column instead of the first (from what I understand, even though the program is laid out over a 6 week period, it's designed so that you can repeat a week anytime you feel you're not ready to progress).
I'm doing the push ups on my cardio days first thing in the morning. That seems to work well for me, but I know others who prefer to do them on their strength training days.