Firstly, and being completely selfish for a second, I was pleased to see the concept of the store.
Secondly, I was encouraged that much of what I have learned in the last 18 months or so of WP7 development (and prior to this with pure Silverlight) has put me in good shape for Metro style development on Win8. (I am less excited about HTML5 from a dev perspective but understand the desire to maintain the legacy thread while at the same time apealling to the widest possible audience).
I have used Win8 on the Acer 1640p from the PDC and found that I adapted to the two interfaces quite quickly. As a developer I can live with the "schizophrenic UI" of the preview (I would like to be able to fire up the old start menu on occasion without resorting to hacks).
In an ideal world I would use the preview as my main development platform but the fact that I can't build for WP7 makes that impossible and probably means that I will spend less time in it than I would otherwise like.
Pleased that MS is still capable of doing 'brave things'- IMO absolutely necessary in the face of the competition and the speed of technological change.
I guess there will be 2 hardware camps for some time to come (traditional PC and new style slate/touch devices) and I do have concerns that MS is trying to cover both with one product. (for most users this is going to result in a lot of confusion)
The actual release should maybe market the same product (Win8) targetted/focussed on the different hardware devices: Phone*, Slate, PC etc.)?