Great hack!
Just installed it, followed the well written instructions and worked perfect on 2.2.1
I tested it on IE on the PC and it works fine...BUT...tried it on IE 5.0 on the Macintosh and when you collapse a forum all the forum titles, thread titles, descriptions and tables below the collapsed forum get squeezed to the left (take up maybe 30% of the left hand side of the table instead of running normally to fill the whole table left to right).
If you have a Mac with IE you can test it at my forum to see it.
http://www.rcuniverse.com
Any idea how to fix?
Also attached some images to match the default vbulletin style for anyone who wants them.
marc