abc_123,
I've been running into the same issues as you with the leg press and hamstring press machines at the gym not being able to keep up the pace. I have been doing back extension exercises instead of crunches since I do different core strengthening routines on different days.
I also had the same issue with losing a couple of reps on each exercise by looking at my watch. I'm only about 3 weeks into it but I'm able to keep 3 cycles of 7 exercises at about the same reps, but don't feel very tired after an hour workout (even if I add 1/2 hour of stationary bike).
I have noticed my pushups increasing by about 2-5 reps a week though.
People at the gym sure look at you funny when your writing down rep counts and weight amounts during a workout.
No soreness the next day or two is nice.