I own a pre A-1 M-40 (and owned an S40 which was stolen :banghead: ).
Excellent pistols all the way around. Well built, accurate, nice ergonomics, both mine have been dead on reliable (only a couple of ammunition related stoppages with the M40 and not once single stoppage with the S).
The only difference between the M and the M-A1 is the plastic parts of the frame (and the manual safety is now optional on the A1). Some like the new grip better than the old one, however I've not handled and A1.
Only issue is the sights ... you either love 'em or hate 'em (I hated them for the first 10 minutes I shot ... then I figured them out and love 'em and wish I could get some for my other non Steyr guns).
Also, during break-in on some of them they have a tendency to eject brass straight back ... kind of annoying, but after break-in of about 200-300 rounds the problem goes away. I haven't had this problem (my M came pre-broken-in by the previous owner, and my S just worked perfectly brand new ... DAMN I miss that pistol
).
I trust my M with my life (and trusted my S ... which I actually preferred both carrying and shooting ... did I mention how much I miss it?).
Anyway, an M-A1 in any caliber should make for a nice duty piece.
On a side note I also own a RAP 401 (which you might be familiar with as they used to be issued to South African police) ... no where near as nice a pistol as my Steyrs.