Fit and finish is equivalent to the M&P and the Glock. The tenifer finish is bulletproof. The three dot sights are not ideal, IMO, but the front is easily replaced by a fiber optic sight and the rear dots are easy to black out. The grip circumference is fairly small, suitable for smaller hands, and very close to the M&P in feel (without the palm swells) which makes it better than the M&P, IMO. The DA trigger is smooth but long and fairly heavy, typical of DA service pistols, the SA trigger is clean and very short, and the trigger reset is extremely short and crisp. It has the best out-of-the-box trigger, hands down. Recoil sensation is very mild and muzzle flip is perceptibly lower. Controls work well, though I do not like the narrow thumb safety. In my opinion, it should be wider, as wide as the STI 1911 safety (so that I could rest my thumb on it). Feeding and function has been flawless. There was one instance of the slide stop pin drifting to the left, allowing the right side of the slide stop to drop down; it was pushed back and it has since stayed put. (I did see another new shooter with another GP6 have failures when bullets got stuck in the chamber. It turns out that you have to size cast bullets...???...Who knew?) Field stripping is different, similar to the Walther PP/PPK, and reassembly is easy only if you have read the instructions in the (included) owner's manual. Read the manual, though, do it three times, and you'll understand it. Blade-Tech is making holsters to fit it, and for magazine pouches order CZ-75 pouches.
Bottom line? I like the Glock 19/23 better, despite the fact that the GP6 would be a better choice for IPSC. For a pistol intended for IPSC Production competition, the STI GP6 is a viable choice. If that was my only criteria, I'd probably pick it over either the M&P or the Glock, and, for IPSC, I'd definitely choose it over a USP.
But - for me - the (too-narrow) thumb safety is a real problem.