This is a pretty cool video. It's a interview that Cobain did in July of 93 and he says that he may have been gay. http://m.youtube.com/watch?v=C1Z2BkZaOQc
He did an interview for the Advocate (gay news magazine) back in the day and one of the major pull-quotes from the article was "I'm definitely gay in spirit." I don't remember much of the actual article or context of the quote (I wasn't that comfortable with my own sexual orientation at the time), but I seem to remember it was more of an "I'm supportive and with you" thing more than an "I'm attracted to guys" thing. He was definitely a complex and tortured soul, and the 1990s were a very different time to be gay, so it's very possible that same-sex feelings were a part of the complexity that drove his drug addiction and depression. It would be interesting to read/watch more interviews with him to get a more complete picture, to the extent that *any* publc comments he made would reflect his true feelings.
People in the Seattle area who followed him believe he may have been bisexual. It's so sad. He was young, but had he hung in there, he could have walked away, had his accountant send him checks, and live a quieter life somewhere. Easier said than done.
He experimented, I think, but unless he said he was gay, he probably wasn't. Me and my friends always assumed he might have been bisexual, or bi-curious, at the very least, but it's hard to say.