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The gun matters not, seek training. Software trumps hardware.
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Smartest thing anyone's said in this thread so far (above).
Re; 22's versus other calibers:
Plus side of .22's:
Shooting a lot of .22 will make you a better shooter faster than shooting other calibers. You are much less likely to develop bad habits shooting .22's. People who are accomplished marksmen and/or instructors will tend to steer you toward the .22. The statement about "outgrowing a .22 in a couple of months" is... umn, I'm trying to think of a polite way to say it... well, let's just say there are NRA grand masters and national champions who find shooting .22's to be highly challenging and rewarding, and still compete in small bore, who have been shooting considerably longer than a couple of months. Generally you will be more accurate with a .22, and it is very rewarding to shoot that way. Others have mentioned the ammo cost issue, which I suppose depends on your budget.
Down side of .22's:
Rather limited as a defensive caliber. If part of your goal is to defend yourself, your home, and your family, AND you do not forsee being able to afford a second gun for a long time, a .22 is not the best choice. There is some "visceral enjoyment" of shooting that comes from the muzzle flash, the recoil, and the noise. .22's will not be as fun in that regard. If you tend to function primarily on testosterone and gut thrills, there are other guns that will be more fun for you.
As mentioned above, there are some pistols that have conversions available, allowing you to switch back and forth between .22 and a larger, more defense-capable, caliber. The CZ 75 is a prime example. Most 1911-pattern pistols (think: US Army WWI and WWII pistols) can be used with a .22 conversion kit. This allows one to practice with the same system of operation and controls and the same trigger feel in both calibers, which is a plus, and can be a bit less expensive than two entirely separate pistols of the same quality.
Most importantly, though, as El Tejon says, go out and find thee a good instructor and get some training. This may give you the chance to rent/try several different guns and learn more about what you like and dislike. A good place to start is an NRA Basic Pistol class. Find one in your area using this link:
http://www.nrahq.org/education/training/find.asp