Softpedia takes Microsoft's Vista to task for it's profligate consumption of computer resources. This one is worth a read, if only for the irony inherent in it.
At the same time, exo-blog takes apart the beta for Vista Service Pack 1 and notes there is no performance improvement available from installing it. I'm not sure how to take this as it is in direct conflict with reports from testers whom I know and respect.
See for yourself.