This week Atalie and I pair programmed our way through a lot of the bugs in searching/ tagging in the edge branch. This break from remixes was in preparation for the new release, which occurred Wednesday. In edge, the search now works for tags on Worlds, Challenges, and Posts. Your query is also checked against the names/titles of all the Users, Worlds, and Challenges (and possibly Post titles, I imagine? I don't recall...).
For the Wednesday release, we hadn't quite fixed the part where you could type in "mar" and still find results for "mary", but it's fixed in edge now, if not on the live site. We merged all that into our edge-remixes branch, and are now working on putting remixes back into the tag/search part of things on our branch. (I also wanted to test out the new release a little, for fun, so I made a fiery pheonix world.)