Actually, the "key lock" is a pretty simple mechanism - I would not worry too much about it. You can completely ignore it if you want.
I got a M9-A1 a couple of weeks ago and absolutely love it. I can pick up a good sight picture with those trapezoid sights much faster than I can the old "post in the notch" style we all grew up with. You might think this is a gimmick, but they really do work (at least for me and some others - YMMV).
One nice feature not often mentioned about these pistols is that the whole "gun" or trigger mechanism can be pulled relatively easily out of the polymer frame to make it extremely easy to clean everything. Much like SIG's new P250, the polymer part of the gun is really little more than a handle and magazine well. The "gun" itself, including the metal slide rails, is a self-contained module that can be popped right out and back in again.
The very low bore axis, combined with a steeper grip angle (than the 1911), produces a handgun that has relatively little muzzle flip as well - which results in less perceived recoil. Overall, I am really surprised now that I have one that they did not catch on more than they did.
By the way, if you're in the market for a good Steyr IWB holster, try these guys: Custom Carry Concepts - this link will take you to his (blatant, but nicely executed) copy of the Comp-Tac CTAC, which he provides for Steyrs - which Comp-Tac does not.