Hey, Revast, can I ask you to censor your first post? I know you're just making a point, but I'm pretty sure the Powers That Be would like to keep the forum free of swearing.
And now, somewhat ironically after asking you to censor your post, I'm going to turn around and say I don't really think you SHOULD censor yourself while writing.
First off, I think made-up swear words are very, very hard to do right. In fact, Jordan is one of the few people whose made-up swearwords I could read without rolling my eyes (and we've had eleven big fat books to get used to his cuss words). A lot of times it seems authors with made-up curse words just come up with things that sound dumb, and if it sounds dumb, I'll be annoyed and wondering why they didn't just say what they mean.
The other thing is, there's a difference between a character who drops the F-bomb when he's closed his fingers in a door, and a character who just says "shoot". So I do think it does, or can, make a difference to your characterization.
I don't think it makes an author look immature, either, at least not if it's done correctly. If a character's gonna swear, let him swear. It's when the swearing becomes gratuitous - when the author is putting the swearing in there just because he can - that it becomes annoying and makes the author look immature or incompetent.
If it's true to your characterization, let it stay there (and only then). You might alienate some people in your audience who are uncomfortable with that, but you can't please everyone. Ultimately, as long as it's something you're comfortable signing your own name to, just do whatever you want.