I joined and it was one of the best decisions of my life. Not only did I end up with dozens and dozens of really good friends, with many of whom I'm still in touch, but all the different committees and activities and programs and such taught me invaluable practical lessons about how to get things done in a group that I have used throughout my career, lessons you'll get in no classroom.
One of the guys who was a senior when I joined (and on whom I had a minor crush) later died of AIDS. One of my pledge brothers came out in his 30s I think it was. Other than that, don't know of any who were gay or bi out of about 150 who I knew while in school, but there must be more.