Regarding MicroSoft's "SourceSafe" product...

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It polls!  There is a notable difference in performance on a machine when you have it open.  Flip to the performance tab in NT task manager when VSS 4.0 is open and watch your CPU usage line climb to a high plateau.  -- MichaelFeathers 

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Regarding the polling, that bug has been fixed; see KB article Q154469, "FIX: Visual SourceSafe 4.0 Increases Processor Usage" at http://support.microsoft.com/support/kb/articles/q154/4/69.asp

If you have to use VSS and VisualStudio over a dial-up line, try "Gnome Hammer", available at http://www.gnomehome.com/, which forces some of the processing into the background, speeding things up tremendously.
--KatyMulvey
[this web page just has a single line of text and no links -- nothing about "Gnome Hammer". Has it gone offline ? Is this the wrong URI ?]