I was surprised when I saw my latest Windows update was approximately 65MB to 427MB. And of course, I thought, it must be the first ever Windows Service Pack for Vista. Indeed it was.
But I did not download it immediately unlike the usual Windows Updates simply because this service pack has been tested by Gizmodo and it turns out that network copy and hard disk read speed will slow. I really have not idea what Microsoft is trying to accomplish here. Make our system more stable but slower?
So unless your Vista keeps acting up on you, wait and see if Windows can do better.
Link