Like it quite a bit, seeing some great potential there.
I'm happy to see Microsoft used the Zune interface as guideline as many, including myself, liked the interface and where "hoping"/"seeing" the possibility of a phone entry to the Zune's menu structure. In this case Microsoft went further even and expanded on that UI just like i feel the Zune interface is an expanded/further developed titanium UI. Thank god we get rid of Touchflo/Sense finally, always hated it, but that's just my personal opinion ofc.
Next to that the new zoom/rendering/cleartype is very nice and a great addition to any OS.
Personally i dont care too much about all the social networking features as i hardly use them myself and suspect europeans overall use these less than americans. However i like the widespread intergration of these things, from the photo app, the Me tile etc. to the automatic selection of contact information.
Hope our great dev's and myself here at XDA will figure out the inner workings of it and be able to polish it to our liking.
my two cents for now