Just scanned a couple of dozen from my to-read shelf into the iPad app. The only books it couldn't find were from a "Tescos special" Matt Smith Dr Who box set (2010). It found the 2008 David Tennant books. The oldest of the other books was 1972, plus a bunch from the 80s - didn't have any trouble with those.
My Goodreads app on my android has just updated and now it has a barcode scanner!!!
Now, that'll make adding books to Goodreads shelves much easier!
Can't wait to try it!