as Pheller mentioned above, I have a '95 GT- V6 5-speed. I got it at 98,000 miles and now she is at 192,000 miles. Never had major issues with it... normal maintance stuff. '93-'94 had some distributor issues so i would avoid those like the plague.
I've been very happy with it. As the age/miles increase, she is starting to show her age.. suspension is shot, engine isn't exactly as peppy as it used to be, and some rattles are showing up. But what do you expect for almost 200k? It will rev to 7000rpm any day and with the right exhaust, it will sound amazing doing it. It handled great when I first got it but with some Eibach spings/Tokico struts, it will be on rails. Aftermarket is fair... not tons of stuff out there but there is some support.
stock 626 rear sway bars bolt up (thicker) and stock Mazda 6 brakes (rotors/calipers) will bolt up and are larger than stock.
I've had it at a few auto-x events and it did fine... has some annoying understeer but I bet the rear bar will aid in the turn in a bit. 28mpg on the highway at resonable speeds- it is geared a bit high so doing 70mph on the highway you'll see about 3500rpms but that makes for easy passing in 5th gear.
I've wrenched on it alot in the past 7 years and have parted out a few so I know my way around them. I wouldn't mind keeping one around for a daily driver... nice, comfy interior, good to travel in. Not tons of power if your a drag guy, but on backroads it's plenty to have fun with and get in trouble. Dunno what else to say... hit me up with any other questions.
The KLZE engine is a nice upgrade and the stock engine takes well to turbo... easy get solid low 13s with a kit and megasquirt. Transmissions tend to crack (the cases) over 300hp. and hard shifting. There are plenty of boosted Probes out there in the 300hp realm too.