Velonews has an article on lactic acid myths.
The punchline re: clearing lactate and acid when going hard - what my swim instructor stressed back in 1986 - exhale, exhale, exhale! Don't even sweat the inhale. Exhale! I found it the secret to freestyle. Didn't take long (well, I did have to leave Michigan!) to find the same applied to climbing. When I observe that "oxygen debt" is slowing me down, I make it a point to do very long, deep exhales like I did swimming. My speed goes up nearly instantly when I start doing that. I am able to push much deeper.
So thank you, swim instructor. Sorry, I cannot remember your name but I will remain grateful to you as long as I am riding. (She was a grad student studying exercise physiology.)