here is my feedback as a Blogger and two questions:
1. Blogger thumbnails youtube videos, and the thumbnail is available in blog feed. Custom search does not thumbnail youtube videos. Youtube video thumbnail is easy to implement and I think it would be a great feature for custom search, too.
3. For some blog pages, mainly archive pages, the automatic thumb may not be good (it is usually from the first post of that archive page). Can you somehow prevent the creation/showing of a thumbnail for a page, for example by using empty content for <meta>?