For anyone that cares.
Addons will break of course till updated but In Windows 7/Vista for example there is a big interface update. It is a little shame they made the interface designs public and Open as Opera latched on to it. It is not a massive way off Chrome for that matter but then all that is open. A consistent user experience at the end of the day is not a bad thing.
Hardware acceleration is still a bit buggy but early impressions - AWESOME!
Im going to stick with 3.6.6 till 4 goes gold. Present version does what I want and there are a couple of things I would like to still be able to use Foxclocks being one of them. Pretty useful for round the world internet gaming
http://www.stemhaus.com/firefox/foxclocks/