Add support for Apache Solr, for full-text searching, faceting, etc. One way to do this would be integrating with Websolr, just as Heroku does.
Also it is entirely irrelevant to even compare full-text-search support in SQL Server. Solr is closer to a nosql implementation. http://stackoverflow.com/questions/3339793/why-are-document-stores-like-lucene-solr-not-included-in-nosql-conversations .. http://www.lucidimagination.com/blog/2010/04/30/nosql-lucene-and-solr/
I would rather see a .NET port of Solr.
Another way to get full text search functionality is to use what is built into SQL Server - http://feedback.appharbor.com/forums/95687-general/suggestions/1893505-full-text-search-support-for-pdf-files-and-danish?ref=title