Yes, a very useful tool. Normally I would say that any clear night is a good night, after all we don't get enough of them, but there was a night recently that, despite it being clear, we packed up and went home. So I expect mostly I would consult these plots to see what sort of night it will be but perhaps I'll eventually feel I can use them to decide whether it's worth going out.
I found an explanation of the plots here.
http://www.bom.gov.au/aviation/data/...ion/skew-t.pdf