This Office Outlook 2007 hotfix is primarily meant for fixing private calendar item crawls performed by the Search Desktop feature. A nice side-effect/noteworthy item is the fact that it also improves performance of large OST and PST files.
Grab the fix here and read the actual KB article here.
In the past, I used Outlook 2007 for my RSS feeds but it became too sluggish with all of my feeds. I am tempted to try it again as my default RSS reader.
Update: This is a brand new Outlook.exe and Mspst32.dll which updates the build from 12.0.4518.1024 to build 12.0.6014.5000.