Has anyone here ever been on Second Life? What did you think?

I went on, and thought it was ok. I made a few friends, and explored a bit. It is amazing what people build on there. The funny thing is that I have seen on tv where several people make millions of dollars a year selling stuff on there. Mostly real estate, but also clothes, houses, cars, you name it. It amazes me because you sell stuff that is not really material, but get real money. How crazy is that? Also, a lot of people have relationships on there with other people, and feel no guilt for there real life partner. What would you do if you found out your SO did that?