Mike
I've been using libjpeg-turbo for months now on both ubuntu 10.04 and 10.10 (x2go clients & servers).
I put it on both client machine & on server assuming it would benefit jpeg cpu utilization and although I don't have the info handy now I thought I'd sent out a couple screen shots of cpu utilization with and with-out libjpeg-turbo installed.
Sorry I can't remember the number off-hand but there was a pretty significant difference
On the client machine that may or may not mean much but on a server hosting a lot of desktop users I figure its a good cheap performance (or capacity) bump depending on how you looked at it.
I "think" the new debian and the upcoming ubuntu may it in their repositories now. I'm assuming other distro's too?
http://libjpeg-turbo.virtualgl.org/
Brian