When I started doing the Insanity workout I just had a somewhat worn pair of running shoes.  Running shoes in general are not good for plyometrics because they lack lateral stability, but worn running shoes are even worse.  As a result I started looking for a good pair of cross trainers and tried these.  I found these to be very comfortable, a good fit, very good cushioning and stability.  It was perfect for all the jumping and side-to-side movements.  I had done a couple workouts in the running shoes and could tell an immediate difference the first time I worked out in these.