Well - if you can wait a bit - Oracle plans to add fulltext indices support for InnoDB with MySQL 5.6 - finally.
Client side the old MyISAM syntax can be used so there's - once 5.6 is released - no longer a need to install any 3rd party plugin.
Maybe just wait a bit until 5.6 reaches production status, then there's no need to play around with Sphinx.
http://www.oracle.com/us/corporate/p...id=rss_ocom_pr