I've been coming to the Pilates Studio for several years. Initially I did mostly mat classes, but more recently I've been participating in small groups, or in Pilates for Riders, or doing independent sessions. I feel that my posture has improved about 200%: standing up straight and not slumping have become the norm for me. I also feel like my sense of balance and my overall fitness--particularly core strength--are way better. Everyone is extremely helpful and knowledgeable. They listen to what you want to work on, to what physical issues or limitations you might have, etc., and work with you, pushing you enough to help you improve but not so much that you risk injury or making issues worse.
If I had more than two thumbs I'd put them all up; but I'll settle for giving them five stars!