I recently "upgraded" to Vista on my laptop.  Immediately, I noticed a few things that were very annoying...  Primarily, it was the file transfer speed between my Vista box and our Windows Server 2003 box.  What used to take about 3 minutes to download now takes well over 4 hours.  In addition, the WSS portal we use takes over 1 minute for the home page to come up, versus less than 1 second.  Yuck.  So, I have to keep a copy of Windows XP around whenever I need to download stuff from our server.  I shut down Vista, swap hard drives (laptop) and boot into XP.  Then my speeds are nice and fast again.

Microsoft recommended that I run the following command as an Admin from my Vista command prompt:

netsh interface tcp set global autotuninglevel=disabled

I wish I could report that it increased my performance, but, alas, I'm still stuck. 

I love the Vista experience, and there's so much to like about the OS, but I've run into so many "gotchas" that kill my productivity that I have to recommend staying with XP for now.  At least until the first Service Pack is released, or they solve the major interoperability issues.

UPDATE:  I did a reboot after the netsh command above and NOW I'm moving quickly!  It worked!  I've still got doubts about the wisdom of moving, at this time, to Vista, but my communication problem with the server is no longer one of them!