UPDATE: This Plugin has been updated, please see the new post, comments here are now closed.
A long time ago Sc0ttClarkcame to me and suggested that his cookie subdomains plug-in & my cookie path plug-in should be merged.... well I've finally done it!
There was a little delay in the release as the initial code only worked for top level .com, .net & .org style domains but a simple "manual" option in the admin screen now allows you to set the domain name, so longer domains like .co.uk can be supported!
All previous functionality is supported, just by enabling the plug-in the path is stripped out you only need to go into the admin page if you want to change the subdomain of the cookie.
The admin page now has a "News & Tutorials" feed (subscribe) my plan is to post articles on how to use root-cookie.