have one, excellent pistol.
for the amount of use the average shooter will put on a handgun, the availability of parts is not a big issue- they rarely break.
holsters for the G23 fit the original M40 perfectly; dunno about the newer A-1 design.
$450 is on the high side of the price range that you might find around the internet, but the dealer's price already has the shipping and his fees rolled into it, added costs that you would need to pay if you purchased from an out-of-State seller.
If the pistol feels "right" in your hand, and fits the type of shooting you enjoy, then it is a good choice. They are quite accurate for a service pistol and have a very low bore axis, so the perceived recoil and muzzle rise is minimal.
They have their own home-brewed internal lock and a manual safety, but neither need to be employed during normal operation.
Certainly a pistol worth considering.