My gf drives an '06 Mazda 3 S sedan, I drive a Mazdaspeed3 GT... Hers has about 23k, mine has about 6k...no problems on either car so far
I liked her 3 until I drove the Speed3...I wasn't real crazy about the hatchback at first, but it grew on me, and have found it is handy to have the extra space. Once I hit the gas a few times in the Speed3 I was sold...quite fun. Watchout for torque steer if you haven't test driven one yet
As far as trim (S vs. GT) you don't get a whole lot with the GT...leather is limited and the S comes with a similar stereo and electric windows/locks/etc. You can get a sunroof on the 3, but not the speed3.
I would check edmunds.com for the pricing, I found they were accurate when I went to buy the car...
As far as reliability, Consumer Reports has rated both the 3 and speed3 as 'recommended', and I think they just recently did a 'sporty cars' comparison with most of the players...
speed3 vs. mini vs. scion vs. civic Si vs. vw GTI...speed3 'won'