Right now our new startup WebPub.com keeps WordPress automatically updated whenever an update comes out.

We have a method to update plugins as well when updates come out, but we still need to finish some key features before we roll that out. We hope to have that ready end of this year or early next. Basically it will allow you to turn on automatic plugin updates for WP, or to be notified when one is available so you can manually update. Plus with snapshot rollbacks in case there is a problem.

We are spending the next 30 days squashing the last bugs and exiting beta, then the next 60 after that finishing the marketplace frontend (which eventually will give a framework to plugin authors to push updates out as well as themes if users allow it),
Thanks, Ben
Co-Founder WebPub.com