Pricey but the best so far.
I've been trying to make my office chair more comfortable and have tried a few foam cushions and a gel-type cushion, all in the $20-$30 range.  They were an improvement over the flatten-out chair cushion but not much.  Since I sit for hours at a time for my job, I decided to bite the bullet and buy this Purple cushion.  Even though it is quite a bit more expensive, I now feel it is worth it since it is significantly better than all the others I've tried.  It has taken some getting use to and it took a few days for the chemical smell to disappear, but now I can sit comfortably for several hours then stand without being stiff and sore.  I'm 6-foot tall and 240 lbs and the cushion size and "springyness" is about right for my size.  I recommend this cushion.
Rating: 4 stars