I did the first two parts, and have taken a break over the holidays (my gym is at the university so not reliably open). I really really love it, and the only reason I haven't started back is figuring out how to fit the longer workouts (stage 1 is short, easy to fit in) with my teaching schedule. Heavy weights feel awesome.
I also track my weights etc on an app (jefit) rather than the sheets. You can add new rules as a routine and log everything right there. I also found an app for calculating weights to load on my bars super helpful (barcalc is what i use).