Echo the sentiments...go around is from 0.1mm upwards :o)
The other thing to remember is that you are probably in the worst position you can be - low and slow - so although must act quickly, make sure you dont do anything stupid. Chuck tried to get this point across in his thread.
As my instructor on my PPL always said all those years ago
"Treat every approach you make as a potential go around"
I have always stuck by his advice since!
J.