I owned an S40 (non A1) for about ten years. Had a bit of trouble with it not wanting to return to battery for a bit, but after a break in period it worked out.
The following pros and cons were my experience only, and anecdotal. I should point out that I think that with proper distributor and aftermarket support, this would be a better gun than the Glock for most any application.
Pros: Accurate, lightweight, and I liked the sights. Felt recoil was much more manageable than comparably-sized Glock. That is kind of subjective, but I found it much more comfortable to shoot than my G22. Bore axis is VERY low.
Cons: Good luck finding a holster, especially if you are a lefty, as I am. I went with Customcarryconcepts.com, and had a kydex IWB holster made. Otherwise, couldn't find much, but mine wasn't an A1. YMMV.
As noted above, the slide is WIDE. Thicker than a Glock. Still concealable though. Trigger reset was a bit mushy on my gen-1, not as positive a "click" you get with many striker or hammer fired autos, but still manageable. The trigger pull itself was shorter, lighter and crisper than my Glock. I wanted a recoil buffer for my S40. Couldn't be found. Also, aftermarket recoil springs were difficult to get, I went straight to the distributor for spares. There was a guy on the Steyr Club forums named Big Taco. He was working on guide rods that would allow you to use aftermarket Glock springs, if you wanted to change your spring weight. People seemed very pleased with his work. Don't know if he is still doing that.
I really enjoyed the gun, but in the end, I needed something that didn't make me feel I was going on a quest to get ANY accessories. As a range gun, or a gun for a righty who can find holsters, it would be great. In the end, someone wanted it more than I, and I went back to my first love, K-frame S&Ws.
It should be noted that my experience was with a gen-1 gun in .40. I'd definitely take a look at the A1 in 9mm, especially at the current prices.