I have already read that article via a link over at Rage3D........Hopefully Microsoft will release the full version to the public sooner rather than later.
Quote from the article
"First up, I can say that there is a very noticeable performance increase. It is obvious that since Microsoft released Vista to manufacturing, it has been optimising the code ever since. (I suspect this revelation will fuel the fires of the people who say Vista was released before it was ready for prime-time.) There’s far less hard drive thrashing and in general the system seems much smoother and more responsive."
Anything that reduce the amount of disc activity just after start-up will be very welcome.
As for the large size....the article does say that the SP1 Beta was integrated into a full Vista installation DVD.The actual SP1 release for existing installations will be much smaller.