I love Core Secrets! Gunnar Peterson, the instructor, is fun and motivating. The moves are very functional. I have both the originals (all on the ball) and a newer set (1 all on the ball, 1 half on the ball and half off, and 1 off the ball). I find that these work wonderfully for recovery weeks, when I focus on balance, core and functional fitness. Then I can get back into more traditional weight work with a bit of extra "oomph" and having worked the support muscles a bit more.
I'm looking forward to the newest ones, which include an upper body workout and a lower body workout.
One thing I find is that there are very few reps for each exercise, but I usually get in extra reps while Gunnar is setting up the move. And I find that the moves in the "Off the Ball" workout and the standing moves in the 1/2 ball, 1/2 off the ball workout really work the glutes and legs in a different way than usual that is very effective. Lots of one-legged squats, 1-legged reaching lunges, the core used for virtually every move.
For those who want nothing less than Cathe intensity, these would be too low intensity. But if you appreciate a variety of exercise intensities, and want to add some effective core/balance/functional work to your workouts, these are good to try.
Though I also find that with these types of workouts, the more you do them, the tougher they seem to get. Probably because you're working more into those deeper supporting muscles rather than the superficial muscles that are usually worked a lot. Also because you can dip lower, reach higher, etc.