Before upgrading to 1.2, I'm pretty sure I used to be able to see the Featured Image sidebar for my custom post types. Now, I can't see it anymore, for existing posts which have it or to add it for new ones. I have the Thumbnail display option checked, and verified that it's not hiding under Screen Options.
I tried checking and un-checking other display options, and those appear just fine. Just not the Thumbnail (and thus Featured Image) sidebar.