I'm a self-published author. Some swear that's the death of a writing career, and perhaps it is. The question of whether self-publishing is a good thing or not truly depends on what you expect to get out of it. For me, it worked out rather neutrally. I can't say it completely killed a writing career because I never had one to kill, nor can I say it launched me to the highest peaks of success. I can say, however, that the experience was invaluable.
The major downfall with self-publishing is, of course, that anyone with a bit of money can do it. Literally hundreds of publishers are ready to "make you a star". Most of those are flat-out crooks, too, but let's put that point aside for now. Even the legitimate companies, who tell you what they're all about, are first out there for themselves, then out there for you. You must understand this if you wish to pursue self-publishing with your "eyes open".
The second downfall of self-publishing is that unless you pay someone to edit your work, the editor is you. This is how 10-12 grammatical mistakes made it through to publishing. Most of those are small comma errors, but a few are more "doh!" worthy.
Write because you love it sounds so cliche, but it's true. Very few gain great financial success, but there's something sweet about the craft of writing itself.
The greatest boon for self-publishing is the opportunity to learn while you play. Writing allows one to ask questions and explore life through someone else. My poor characters go through a lot, but sometimes they ask for it. Getting into the mind of a psycho bent on controlling a planet and a spunky ten-year-old from GA are two completely different things, yet both types of character have something to teach us about their world, which by extension also teaches us about our world.