One of our early WP adopters asked about tracking access stats on their new blog.
Worked with Ian to identify a way to easily enable Google Analytics for WP MU.
We found: http://wpmu.org/google-analytics-for-wordpress-mu-single-blog-and-sitewide/
This will allow us to view a report across all blogs but also let individual blog admins to set up and access their own reports for their own blogs.