I think the points have been hit pretty good, but I've got to chime in as someone with some rotary experience. The 04-05s Rx8s had some reliability issues that resulted in a lot of engine failures, which have been resolved. The bad press/image is why Mazda retroactively extended all Rx8 power train warranties to 8 years 100k. What was pretty cool of 'em was that they also paid back any owners who had to pay out of pocket for an previously "out of warrenty" repair on their engine. They also had some flooding issues and such, mostly resolved with software fixes.
That said, if you look at an 06+ you'll have none of those concerns, but the price reflects that a bit as well.
The "needs a lot of attention" thing is really beaten to death as well. I would recommend checking your oil about every 1000 miles, though. For normal use (commuting, fun driving and some autocrossing) don't worry about premixing or any of that noise.
With my 07, if I beat it like it owes me money, I seem to get about 19 MPG. If I just "normally" (for me) drive it, I can get about 20.5 or so. I normally beat on it!
Maintenance for it should include redline every time you take it out, after you warm it up, it's just good rotary maintenance :)
As far as longevity, my last Rx7 (an 86 non-turbo) had over 235k on it when I sold it, with the original motor as far as I could tell. My dad's 85 that he retired due to rust had about 150k on it, we just fired up that engine a week or two ago in his new 83 shell. The boosted engines stock seem to go about 130-140k without an overhaul, though expect to lower that to 100k or less if you start upping the boost.
Oh, I will add that in my Rx8, we can fit 3 adults and a baby in a seat for a day at the autocross pretty comfortably.
1 Mazda == Good. 4 Mazdas == More Gooder.
) for 2 or 3 years with their "minimal" (read: lack of) proper mechanical ability, Id say a relatively unmolested version in the right hands could last for quite some time!
