It's definitly worth trying Rated 4 out of 5 stars
Since new Firefox brings fancy TabCandy interface and Vertical Tabs is aiming towards 4.0 release...
I think it's definitely good idea to go "close integration" road. And should benefit both Firefox (bring "useful" to all that candiness) and Vertical Tabs (nobody likes reimplemented features - TabCandy will bring groups to Firefox).
* all groups and tabs are displayed
* VarticalTabs groups == TabCandy groups
* DND tabs should add/remove/move between groups