Let's keep in mind we are comparing client OS's. There are so many things that corporate PC/LAN add's to clients. It's an interesting comparison in theory, but not quite like looking at Server 2003 v Server 2008.
What did they add when you were upgraded, my work PC is always killed by BESClient (uses about 25% CPU for 5 minutes and runs every 15). I'd run something like sysinternal's Process Explorer to see if memory or CPU are different. Remember, ultimately SS is designed to run on a server OS, a client OS is useful for debugging scripts, but not performance testing (that's why we provide developer's with dev boxes ). There are too many things that run on a client OS to be able to make any decent judgement.
Just for kick and giggles, try stopping un-needed services and see how performance changes. You might be surprised how many extra services will kill performance especially when CPU cycles are at a premium.
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