Information Week has been running a "Rolling Review" of different DLP products in the marketplace. Of the 6 products they reviewed only two of them stood out. RSA's DLP Suite and Symantec's DLP Suite were the best of the products they reviewed.
Here is the summary of the review: http://www.informationweek.com/news/security/privacy/showArticle.jhtml?articleID=219501230
Also here is the specific review of Symantec DLP: http://www.informationweek.com/news/security/attacks/showArticle.jhtml?articleID=218900115
Enjoy and drop me a note if you have any questions in regards to Symantec DLP