This was just my experience, but after using stock Android on a phone and a tablet for about a year, I found the Kindle Fire HD basically unusable when I tried

This was just my experience, but after using stock Android on a phone and a tablet for about a year, I found the Kindle Fire HD basically unusable when I tried it out. I couldn't get it to do anything I wanted. It felt like a thoroughly crippled OS to me. You can only use Amazon's tiny app store (you can get around this but it's not very secure). And as other commenters have pointed out, the Nexus 7 seems thinner too.