A new faceting algorithm has been committed to the development version of Solr, and should be available in the next nightly test build (will be dated 11-25). This change should generally improve field faceting where the field has many unique values but relatively few values per document. This new algorithm is now the default for multi-valued fields (including tokenized fields) so you shouldn't have to do anything to enable it. We'd love some feedback on how it works to ensure that it actually is a win for the majority and should be the default.
-Yonik
