Okay, I'm now a seasoned veteran of handgun ownership (3 weeks) so I thought I'd post my observations so far.
First, the Sig SP2022 that I purchased for my one an only handgun is a tremendously fun gun to shoot. Bought it, stepped out to the range at the gun store, got a five minute tutorial from the owner and was knocking down steel plates at 75'. I'm told that is a very respectable distance for handguns. As of today (3 weeks later) I went through several passes of 6 plates at 75' and went 6 for 6 many times. I even had other guys looking on making me nervous and still hit them all. On top of that, I am feeding this Sig the crappiest ammo they have. $9 for 50 rounds (Ultramax remanufactured ammo) and this gun has not malfunctioned once in over 700 rounds. Consider me a Sig fan.
To my point about 9mm. Your first gun needs to be enjoyable to shoot as well as affordable to shoot. I have friends shooting .40s&w and .45ACP and complaining about the cost. 9mm is cheap to shoot, doesn't hurt your hand and will allow you to practice more. 9mm into center mass is way better than .45ACP sailing through the air and missing any day. If you're a better shot because you've practiced more I think you throw the whole stopping power conversation out the window.
For the guy buying his first gun, get a 9mm with some type of decocker and you'll be having some serious, safe and affordable fun at the range. You'll spend so much time with that gun, you'll know it inside and out when a crisis arises. And, realistically, the chances of us getting in a gunfight are slim. The opportunities to have some fun at your local range are much, much greater.
After shooting for less than a month, I'm entering my first steel plate match tomorrow morning. I won't win, but I guarantee that I will have fun and not go broke.
The German Army took over half of Europe shooting 9mm so don't tell me that it's for wimps. Those are some thoughts from a noob shooter for what they are worth. I don't regret Sig and I don't regret 9mm.