That should work. Conditions really haven't changed since vBulletin 3 and 4. If that isn't working change $vbulletin userinfo to $User. The $User object is will have a larger scope.
There is also a <vb:usergroup> tag in 6.0.4 and 6.0.5. It is described in the 6.0.4 Release notes but it has the syntax of:
Code:
<vb:usergroup groupid="2">Your are in the registered usergroup.</vb:usergoup>
<vb:usergroup notgroupid="2">You are not part of the registered usergroup.</vb:usergroup>
// You can also check multiple groups:
<vb:usergroup groupid="X,Y,Z"><!-- Custom Code Block -</vb:usergroup>
