After reading IGx thread on BW training I recalled that my wife bought a pair of gymnastic rings more than a year ago. I got them out and hung them on the bar of the power rack. My younger daughter joined me, and we played with various stuff: dips, pullups, pushups, Bulgarian pushups, Ls etc. Very cool and very taxing. BW exercises are really good, either for variety or even for as stand alone stuff for muscle building.
When I was at medical school I did some gymnastics. Nothing fancy or too advanced, but I could do a trick or two. Spring preparation for the beach was done exclusively with BW exercises and it was very productive in terms of visible muscle. Handstands and summersaults on top of that earned a lot of respect from friends and made female couterparts more welcoming.
I also remembered something interesting. In 2003 I joined Kung Fu school in Johannesburg. Their methodology was not scientific at all: 2/3 of the session consisted of very intense GPP and the last 1/3 was devoted to technique and sparring. Basic principles of training state that it should be done otherwise. Never mind this though. We did literally hundreds of pushups, always to failure. After a few weeks I noticed at the time that my arms became considerably larger, even though I did not touch a weight. It seems intensity - forced BW reps - did the trick.
That's not to say that I am the proponent of HIT or Mentzer's methods in general. For one I am too lazy for that, and volume approach is the preferred method for me. But it works, no doubt.