We're investigating using Solr for our site, which uses WordPress and BuddyPress, with WordPress in multisite mode. There's also a MediaWiki.
So, we want to replace the WP search with one that covers BuddyPress, the main WordPress site, the WordPress network sites, and the wiki.
Can solr-for-wordpress do that? If not, can it be modified to do so? Happy to put some time into it, if this plugin is a good starting point. Happy to feed updates back as well, if that's useful.