First of all, thank you for having the common sense to ask me to review this product after I had actually received it and used it for awhile. We are impressed with the style and quietness of the PURE 311. The sensors in the 311 are amazing. When extra filtration is needed (i.e.: higher fan speed), the transition is flawless. And, after the 311 has done what is needed, it flawlessly returns to being very quiet. My wife and I are very pleased with our purchase of the 311.