I, just as an end user, would be interested in this.
Whether it's needed or not (I think it is), it would be cool for GLBT websites to differentiate themselves, thus becoming more marketable, easier to find, etc.
And honestly, might help ease some confusion when "gay-sounding" domain names are actually some random product. And Im trying to remember the example here but it seems like it was something like
www.labrysworld.com (maybe?) that sounded really lesbian-friendly but it was actually a gaming site.
I dunno, but I know if .gay ever happens, I will be in the poorhouse.