Here's a study I saw about DBS working better than meds alone. Not sure if it's been posted here yet or not but I couldn't see it so thought I'd post it. There's other good info there too.
http://www.epda.eu.com/news/medicalPharmaceutical.shtm#
Medtronic's Activa® DBS therapy improved quality of life and motor function significantly more than medication alone in first head-to-head trial