I owned one, and honestly it was one of the best cars i ever owned. It was stylish and always got looks no matter where i went.
I had an 04 GT 6 Speed with BOSE and the bodykit and sunroof. It handled just as good or better than any Integra Type-R or S2000 ive driven. Power was a bit down, it felt like a RWD ITR IMO. Lots of revs not a lot of power. it was a ton of fun to drive though it wasnt SLOW by any means and you could pass people easily. The gearing i always thought was perfect it was short geared when you needed it around town and tall on the highway.
The only thing i didnt like was the fuel mileage, it was god awful, i got 16-18mpg around town.
I put exhaust on mine and Underdrive pulley set and it was a good change. My friend had Intake on his and it def seemed more throttle responsive.
I think what killed it was by 07-08 people new they were having problems with the automatics blowing up. The fuel mileage was terrible compared to other cars in its class and around 2006 into 2007 was when the gas crunch hit. I also heard a lot of storied of MAzda doing everything they could to get out of the 100,000 mile warranty they had extended to all RX8s. They just became like every other older RX-X, cool cars if you were prepared to keep up the maintenance.