I hate them, it's one thing to watch anime/read manga on your own time, but this, no thanks.
No the whole thing seems a bit silly to me.
Maybe, it depends on the situation and who I'm going with.
I may attend them for a day or two, if there's one going on.
I love them, and attend them whenever possible.
I've never been to a convention, I don't really hold an opinion on them.