I still think shooting yourself it's one of the best ways to do it, it's super fast and painless, you can stuff your face before, drink an entire bottle of vodka and it won't affect the result. I would love to have one too.
I mean, you're mostly right except for all the things that can go wrong. I would add an asterisk to your post that reads *only if done properly.
There are so many ways a self inflicted gunshot can miss and instead of dying you are horribly disfigured and disabled. One time I was camping with friends at the rainbow gathering, and we ran into a guy who was missing his face, he basically still had eyes but the rest of his face was a mess, it looked like hamburger even after plastic surgery and healing... He had to talk through one of those boxes in his throat like when people smoke too many cigarettes. He had to smoke cigarettes through a hole in his throat, he didn't have a mouth.
I am not a judgmental person, but that was difficult to look at. I think it traumatized me in some small way away from ever considering death by self inflicted gun shot. He explained to us that he used a shotgun, and still failed. I was very surprised by the guys disposition, he said he was happy and glad to be alive, etc.... I can only imagine how frustrated and feeling like a failure I would feel like after that, it would only make me much more depressed and wanting to die...