[kovidgoyal]

1) adding isbn extraction from PDF files is possible. There's some partway code to do that in calibre already. I haven't completed it as I have higher priorities.

2) Sort by date to locate newly added books

3) select multiple books and click the edit meta information button to bring up the bulk edit dialog, there's no need to navigate menus. Since after initial import most people aren't going to be doing bulk metadata edits I dont really see this as particularly important, but I can be convinced otherwise if someone submits a patch. Personally, I'm not interested.

4) Some duplicate detection is in the works and again if you want more, submit a patch. This is not something I am personally interested in.

5) If you want to browse books with full details, just click the lower pain, at which point it becomes a standalone window with next and previous buttons. The same is true for the cover browser (via a preference)

EDIT: Oh and support for custom fields is happening right now