I own the M9A1. The Styer is unique in it's exterior design. The grip angle, the trigger reach, the low riding slide, the trapezoidal OEM sights make it different. The trigger shoe has a wide face with a shallow curve. The trigger is much better than an OEM Glock or XD. The trigger break and reset come close to, but not quite as nice as the PPQ or VP9. The slide is wider and more squat than other 9mm pistols. The slide is wider than a Glock 19's slide, and is more comparable in width to a large frame Glock's slide (20/21). Just looking at the grip from all sides, it doesn't look comfortable. Once in the hand, it feels right.
Lack of aftermarket support is the major challenge in owning a Styer M9A1. Want to change the sights? I think only Trijicon makes 3 dot night sights for it. There aren't as many choices of holsters. If I ever decided to put it in the carry rotation, I'd have to get a kydex holster made locally or try to make it myself. The next challenge is the trapezoidal sights. At first they're a bit frustrating, but it gets easier with more trigger time.
I've been through all the usual polymer framed striker fired handguns: Glock, XD, Sig 320, Walther PPQ, H&K VP9. After a while, they all start to feel like the same old thing warmed over with a new slide cut, modular grip, or the latest end-all-be-all trigger. My current polymer framed lineup includes three Glocks and the Styer. The Styer M9A1 is probably the last polymer framed striker fired pistol I'll purchase.