I bought a 2004 rx8 about 2 years ago as a back up track car, and a car I'd feel comfortable letting my novice friends drive if I could convince them to go to the track with me.
The car had about 100k on the chassis, and about 35-40k on the motor. I think I paid $5500 for it. I didn't have particularly high hopes for it, it was just supposed to be a cheap backup and something to use to bribe people to come with me.(yes I have to bribe people to hang out with me!)
Fast forward a couple years and in addition to it's intended purpose, I have totally fallen in love with this car. At least 15 different people ranging from first timers to seasoned racers have done multiple track days in it. I've driven it myself on track a few days, and even run(and won) a few TT events in it. (It's close to stock so it can run in the lower classes)
Everyone who has driven it, including me, has enjoyed it thoroughly. It's also been by far my most reliable track car by a long shot. Maybe I've just been lucky, but it seems to love the high rpm's it sees on track. Other than consumables, and one $15 dollar solenoid that may or may not have even needed replacing once it cooled down, it just runs. Additionally, I can run laptimes within a couple seconds of my heavily modded e46 330i(that I probably have 10x the $$ in)
It now has about 106k on the clock, with virtually all of the additional mileage coming on the track, and doesn't seem to be any worse for the wear.(other than a few dings and missing trim pieces from a couple off track excursions - not the car's fault though)
If you do take the plunge, and you should, I'd swap out the springs for something stiffer and a little lower (I have the eibach pro kit) and the sway bars(I have the Hotchkis front and rear). It had a bit of body roll with the stock setup, and these easy mods took at least 2 sec off my laptimes on a 2.27 mile track for <$600 and a couple hours installing them. I also bought lightweight track wheels, but when I weighed them back to back with the stock wheels, they were exactly the same, so save your money there.
I just love my rx-8!
(with all of that said, it was consistently lapping withing 1/10 sec of a relatively stock NB miata which did have a new motor, minor suspension tweaks and some weight reduction. I think the driver of that car was a bit better than me though)