Pilates

I have a Pilates DVD and I know a few people who have done it, but I never have. I know it's good for core strength and controlling your breathing and movements but I have a couple of questions. How often should you do it in a week and how quickly can you see or feel results? Should you combine it with cardio or just do it alone as your workout for that day?

Right now I go to the gym 3-4 times per week and I do cardio and weights. I'd like to start Pilates and Yoga, and I would like recommendations of how often to do each. Thanks.