"Network Admin" -> Sites -> Sites -> [Enter part of a blog/site name] -> Click 'Search'
Nothing comes up. I have to enter the full name of the blog to get it to show that blog. This is VERY inconvenient and we view this as a bug in WP 3.1. This, humorously, results in a search engine that can only ever show one blog, which defeats the purpose of a search engine in the first place.