I just installed page_preview in my Radiant 0.9.0.rc3 installation and while it seems to work well, it doesn't look as if page_preview supports 0.9.0's new look. I can send you a screen shot if you want.
Do you have any plans on refining the UI a bit (in particular, placement of the "Preview" button)?
We have no immediate plans to upgrade this extension, but would gladly accept fixes so long as code/spec quality was approximately as good (bad?) as the rest of the code/specs in the extension.