For all of those with HTTP 1.1 compliant browsers that support GZIP (most new ones do, i.e. IE6 and NS 4, 6, 7), you should see a noticeable difference in page download speeds. Especially for non-broadband users on a 56K modem. The forums now GZIP (compress) each page as a GZIP file and send it to you in compressed form. Your browser then unzip's and displays it.
For example, I tested one of the threads using a remote utility. Without GZIP it was 108K. After enabling the GZIP functionality in vBulletin on only level 1 it dropped in size to 18K. Not bad!
Let me know if you notice the difference everyone (especially from our modem users).