I have an extensive library for my ebooks, and even more actual books on my bookshelves, but using calibre for them all wasn't the best option for me. I use Book Collector for my books (available at
http://www.collectorz.com/book/). One of the reasons I chose that program was because I can use my barcode scanner to scan the isbn barcodes from the back and then it will find all the metadata details online like calibre does. It was quick and painless and I did bulk lots really quickly. Another feature is the ability to import from spreadsheets, so if you already have a lot done that way it could be a nice easy import.
Cam
PS, I think would work ok with an ipod or iphone as the scanner, but haven't actually checked