This mattress topper is amazing!  I got it for my five-year-old pillow top mattress that wasn't quite cutting it comfort wise.  I was having joint pain and generally having a hard time sleeping.  I got this topper and unfolded it and watched it come alive and grow to the full four inches in about an hour.  I did not notice any odour and I have a sensitive sense of smell.
  It has made all the difference!  I used to be lucky if I got three hours uninterrupted sleep now I'm up to eight or on one lazy Sunday ten!  It does make my bed very high (32") and I need to use deep pocket sheets which isn't a problem.  It does drift a bit but that is easy enough to fix when you're making the bed.  The cover is tidy and gives the topper a high-end look.  If you are on the fence and are looking for an incredible nights sleep get this topper!