LOL, the responses to these types of threads crack me up. But I'll throw in my $0.02 anyway, lol.
Reliability - most any modern pistol is going to have at least reasonable reliability as a group, so the whole "X pistols are junk, Y's pistols are super duper extra reliable" mantra is just silly, they have all had issues at one time or another, and they all work to resolve those issues as quickly as they can. Even Kel-Tec pistols have a pretty reasonable reliability record on the whole. What you need to be concerned about is the individual reliablity of YOUR particular pistol, whatever brand you choose, you need to run lots of ammo, of many different types through it until you are 100% comfortable it will go bang every time you pull the trigger.
Choosing the right pistol for you - Just about any modern pistol from one of the big names will be at least adequate for anyone, Glock, M&P, Xd, Sig, etc etc, but they all feel different both when held, and when fired. This is why you always get the recommendations to shoot every different pistol you are considering. For me, Sig makes very nice guns, but the grips tend to be too big in my hand, making them slightly uncomfortable, though I shoot them very well. Glocks, I like the trigger, and I shoot them reasonably well, but the squareish grip and the the angle of the grip make its point of aim unnatural for me. Xd, I don't like the grip safety, and the high bore axis makes the gun "flip" more in recoil compared to other similar guns. I chose the M&Ps because they fit me the best, and I shoot them the best out of the group. The trigger is a sore point for a lot of people, but you aren't doing bullseye shooting at 75 yards anyway, and it smooths out after a few hundred rounds anyway. Plus, its cheap, and easy to either improve the trigger yourself or get an aftermarket sear (local guy makes a really good sear for like $30). Plus I'm a lefty, so the ambi controls on the M&P were a big selling point for me.
The main point being, as others have said, shoot them all and pick the one that you shoot the best and are most comfortable with. Though, Scooter70 and I have taken people to the range for them to shoot his G19 and my M&P9 and 9c, and so far the M&P is 3 for 3 with the people we've tried this with....
On Edit - I wouldn't be too concerned about "aftermarket" either. There are only a few things that are important for the typical owner anyway. The vast majority of the aftermarket stuff out there is for the "gamers" (like IPSC, etc) and the mall ninjas. Things like good sights/night sights are available for everything, even red dot sights if that's something you want (though, done right they need to have the slide custom machined anyway), and pretty much all of them have a standard rail under the barrel for lights, lasers, whatever.
On Second Edit - just to hit on it again, but Scooter's post was spot on, whatever you get, practice practice practice. Get your CPL, get good training, and shoot as often as your schedule and budget will allow. A defensive pistol will do little good if you don't know how to employ it properly, and haven't practiced it enough to where it is second nature to operate in a stressful situation.