Being a cosplayed is a little like being a celebrity, for an hour or two. It's also like a giant costume party, where you get to put your creativity into overdrive, and then hang out with a bunch of other people that do the same.
Trying something new. We've been playing with themes and modifications to Totoro for a few years now. Totoro gets a sabbatical next year, while we work on completely new projects.
I'm best known for Totoro (and some variations on Totoro), although we do have a stable of less popular costumes we also wear.
It's a creative hobby I can do with my friends, where we all get to contribute something different, and learn something new.
We did't really have any when getting started, we were stumbling blindly on our own much of the time.
There are 15 ways to solve a problem. If you ask how to do something and someone says "X", "X" is just one of the ways to do it. Try to solve it using skills you have. On of the most interesting things for me to talk to other cosplayers about is the multitude of ways people approach similar problems.
I haven't run across much negative. Drunk people holding open containers of alcohol charging my big costume for a hug . . . which was solved by having aggressive and protective handlers. Every now and again running across someone who doesn't like big/popular costumes at a convention because they cause traffic congestion in the hallways . . . I just ignore those folks.