One other thing to consider...
.45 ACP is going to limit the number of rounds you have available. The newer .40 S&W round is making a run at the .45's reign as king of the self defense rounds. If you look at the terminal ballistics for the .45 ACP and the .40 S&W in high quality self defense and law enforcement ammunition, you'll note that most of the .40 S&W rounds now outperform their .45 ACP counterparts. These rounds provide the same or better stopping power in a smaller cartridge that allows for about 4 more rounds in the same size weapon (generally speaking). While the .40 S&W round is not as cheap as 9mm, it is generally cheaper than .45 ACP still.
As for the pistol itself, I shoot a Glock very well, but I find that I don't like the way it feels in my hand. As a result, I opted to go with the Springfield XDm in .40 S&W because the gun feels fabulous in my hand. You need to also consider whether or not you want a full size, compact or sub compact. This is often determined by your intent to carry concealed or not.
All in all, I'd highly recommend that you attend at least one gun show before you buy so that you can feel all of the different brands. Find one that feels the most comfortable to your hand, that points naturally, and that you can operate efficiently.