It's not a good thing? Do you guys even know the definition?
Please oh please do not go to Japan calling yourselves that.
People will avoid you like the plague.
They already find teenage and 20 year old Americans weird to begin with.
I think just about everyone on here understands the connotations of the word 'otaku', both in Japan and elsewhere. And we definitely understand Japan does NOT = anime. Most people there do find it weird and creepy, especially if you like it and you are older than 12. And it is NOT a large part of the culture. But that doesn't mean that we here cannot use that term amongst ourselves as a term of endearment, as @ShinigamiSan said. We have found something that means so much to us and have found people that also find those values. I think that is awesome. I personally love anime and it has meant a lot to me and actually helped me get through some quite terrible times by showing me strength and friendship and laughter when I really needed those. It's a place where those values lie so that if I ever lose sight of those in myself again, I know I can simply see anime and find them again. However, despite my love and the meaning I have found in anime, there is no way in hell I'd go to Japan just for the anime, or really even say those terms. There is so much more to Japan, and the Japanese culture is very reserved and circled around making sure everyone else around one is comfortable. As such, since anime does make most uncomfortable, I would avoid that topic there, unless it was brought up by another first. Most people here understand that, but here we are amongst those others who share our interest and nerdiness, so there is no harm, and usually affection and camaraderie, in calling one another, and ourselves otakus.
I think it's a term that fans find endearing like @ShinigamiSan said. While there are negative connotations that exist, people who are part of the fandom just see it as a term that brings people together to enjoy anime.
No offense, but it's not like Japan doesn't use terms we use incorrectly either. It's a two way street. And as far as the word Otaku goes, I'm pretty sure 'most' people understand the original meaning. :D As you can see people use it their own way. Won't be the first or last time that happens.