@ kovidgoyal: great piece of software!
I guess an option for those who are interested in knowing a book's
physical page count would be to search for the ISBN number on
http://isbndb.com and use the tag field within the Meta Information section of Calibre to record the information returned. This is what I have done and it is useful.
I would love to be able to have Calibre tell me the page count, but I can see the problem with that based on the varying file formats out there for eBooks.
Another option is to open each eBook on your device, get the page count, and then record it as noted previously in the tag field within the Meta Information section of Calibre.
On a side note, I believe ADE gives you the page count as it only works with the EPUB file types.