Mazda3 owner here!
My car: '05 Mazda3 SP23 (special edition) 5-door hatchback, 2.3L I4, 5spd. trans.
My wife and I purchased this car in May of '05. I did quite a bit of research on it before we purchased the car. What really impressed me is that it's supposed be an economy car, but yet it is so much more.
First off the styling is so much better (IMO) than any other economy car out there. Plus, the list of options is better than any other economy car. Our's came with 17" wheels, 4-wheel disc & ABS, clear lens LED taillights, black leather interior w/front heated seats. Also came with electroluminsent gauges, 6-disc CD-changer, Sirus satellite radio, manually adjustable projector beam HID headlights, rain-sensing wipers, side-curtain airbags and much more.
We paid under $20K for the whole package, but I think most 3's are probably going for $17-18K (average). For the price, you really can't beat it (IMO).
Let me address a few things I've seen other people talking about.
Resale - I could care less because I'll be keeping this car for at least 10 years.
Fuel Mileage - The automatics, for whatever reason, aren't getting very good gas mileage. However, they went from a 4-speed auto to a 5-speed auto in 2006. We have a 5-speed manual trans. I have to say, I'm more than impressed with the gas mileage. I keep very strict records of every tank of gas. The lowest we've received is 26 MPG. Over the life of the vehicle, we are averaging right at 30 MPG. The last two tanks I've filled up have been 31.5 and 32.6 MPG. Again, the gas mileage is great for us.
Reliablity - The 2.3L I4 seems to be a great engine. If it wasn't, I don't think you'd be seeing them put it in both the MazdaSpeed6 and the upcoming MazdaSpeed3. We are just about to hit 20K on our Mazda3. We've had only a couple very minor problems that required a dealer visit (glovebox rattle - fixed, squeaky shifter - fixed, dusty rear brake pads - fixed). I really do not see reliability being an issue with this car.
Cartridge Oil Filter - During the first oil change at 1,000 miles, I switched the cartridge style filter out for a spin-on setup. The 2.0L I4 uses a spin-on setup, so all you have to do is replace the cartridge mount on the 2.3L with the spin-on mount from the 2.0L. It's a 10 minute swap. With the spin-on setup, I now have many more choices as far as brand of filter is concerned, and best of all, I can buy larger filters.
Overall, we absolutely love this car. When we were shopping for one, I wanted the sedan and my wife wanted the hatchback (easier for grocery shopping). Since I got to pick the manual trans, she got to pick the number of doors. Now that we have it, I'm sooooo glad we went with the hatchback. It is so handy and has so much cargo room. We are both amazed at how much stuff we can cram into the back, especially with the back seats folded down. Plus, now I think the 5-door hatch looks better than the 4-door sedan.
Driving the Mazda3 is a blast. The car handles like a dream. I was blown away by the handling the first time I drove it. Coupled with the 5 spd., it doesn't get much better than that. Even with only 160hp/150tq, the car feels like it has plenty get up and go. Would I like more power, definitely, but who doesn't always want that.
With all the great things we love about this car, I truely think it is the best OVERALL car in it's class and is the best "Bang for your buck!"