I also have back and neck problems and ab circuits has helped them. Which is weird, becuase usually my neck gets irritated if I do unsupported situps-I always have to rest my hands behind my head for a little support. Most of Cathe's exercises have your hands free and I forced myself to do them that way and my neck has gotten stronger. This is the first time I've been able to do situps without my hands supporting my neck. I don't know what your neck problem is though. It might aggravate it. But it has helped me.
The workouts are each about 15 minutes long.
I love the yoga and pilates abs-they incorporate a lot of stretching and really help my back. They are the 2 easiest workouts and also easy to modify. The ball abs are really good too, until you get to the pike portion which I am still struggling with! Weights and plates is just the hardest darn ab segement I have ever done. The preview on youtube gives you a good idea of all the routines I think. Med ball is pretty easy if you use a 2 pound ball like I do (I've ordered a 4 pounder), and No Equipment is pretty basic ab work with some new twists.
Overall I love ab circuits and it they are now my favorite ab workouts EVER. I have gotten so strong- I can hold planks, side planks, do a full situp holding a stability ball or med ball. I can't believe how much stronger my core has gotten doing these workouts.
Beth