The 2006 add-on pack will not work directly with SS2008 BUT VSTEP is converting the add-on pack to a 2008 add-on which is going to work with SS08. If you already have the 2006 add-on, you will get the 2008 add-on (the 2006 conversion) for free.
I do not yet know when it will be ready.
Regards
groennegaard