I always tell my patients, "You can't change what you don't monitor." For the first time ever, I'm beginning to understand EXACTLY how stress and diet affect my sleep and sleep recovery. I've always suspected it, but now I have the actual hard data. With the sleep function alone, I've improved my sleep by 25% in the past two weeks since I've had the device. The only knock that I can give it isn't related to the device itself. It's simply the blue and white bands. They are very difficult to attach and, sometimes when you think you've attached it correctly, it will fall off of my wrist. Needless to say, I don't use those bands, which is a shame. If those bands were exactly the same as the black band, everything would be fine! Again, the device itself is amazing. I absolutely love it, the metrics it tracks, and the positive impact it's having in my life in such a short time. I can't wait to see what life is like after wearing it for 6 or 12 months. The extra band issue is the only thing keeping this from being 5 stars. Dr. B