Here is the first alpha version of your WPMU DEV SEO plugin you were waiting for.
It aims to take care of every SEO option that a site requires, in one easy bundle and works with the latest versions of WP, Multisite and BuddyPress.
Automatic Links: allows you to automatically link phrases in your posts, pages, custom post types and comments to corresponding posts, pages, custom post types, categories, tags, custom taxonomies and external urls.
Title & Meta Optimization: allows you to optimize title and meta tags on every page of your site.
SEOmoz Report: provides detailed and accurate SEO information about your Web pages. It uses the SEOmoz Free API.
XML Sitemap: generates an xml sitemap which helps search engines to better index your site.
Drop it in your plugins folder "/wp-content/plugins/" and activate it via your admin panel.
Test it, have a play and let us know what you think so that we improve it based on your suggestions.