Jeff over at GunBlog.com has one, and loves it. You can read his review at http://www.gunblog.com/mgi-recoil-reducing-buffer-review/
Caleb over at RomeoTangoBravo.net also has one and has very good things to say about it. You can read his review at http://www.romeotangobravo.net/2011/07/mgi-rate-and-recoil-reducing-buffer.html
I got a MGI Recoil Reducing Buffer recently as well. I haven’t had the opportunity to take it out to the range yet. I do have to say that installation was rather straight-forward. The hardest part was getting the D-Fender o-ring installed over the extractor spring and reattaching the extractor to the bolt. Look for a review of the MGI Recoil Reducing Buffer in the near future. Until then, Jeff and Caleb should have enough to satisfy you.