The 21 page document can be found in both XLS and PDF format.
Both can be downloaded from Microsoft
In case you don't feel like sifting through 21 pages of Microsoft's PR team at their finest, I took the liberty of summing up the summary. Basically, Microsoft took in a lot of user feedback, and mushed it into Vista Service Pack 1. Service Pack 1 addresses a ton of specific reliability and performance issues. Microsoft even went so far as to re-do the Vista kernel.