The script needs updating: replace adC by Bu.y3 in the script source code. Then the whitespace is gone again.
As of 5/15/12, the script no longer removes the white space in emails again. I like how streamlined the script is, without any unnecessary calculations.
Ninja edit: Using ver. 14.0a2 (2012-05-08) of Firefox(Aurora) so it's current, too.
works fine with FF 8.0 white space gone too
this is a simple extension that fixes the 1 problem with the gmail design in my opinion. Highly recommend it.
The whitespace is still present in all gmail display views (compact, cozy comfortable) in the latest version of Chrome.