I've been using Delicious Library for a little over a year, and have ~1200 books and 800 movies cataloged. It works well, and with the portable barcode scanner I purchased from them, inputting new books/movies is a snap. I pick up the scanner, wave it over the book's/movie's barcode, startup Delicious Library and it adds the item(s) to the database automatically, downloading the artwork from the web.
The only downside I've had is its terrible printing functionality. My library is so large, I typically keep a printout lying around for ready access when I want to select a book or movie to view, but that functionality forces me to continue to maintain my old Filemaker Pro database manually, which is a pain.
Late last summer, they said they were working along on version 2.0, which was supposed to incorporate a robust printing facility to format output reports from the database, which has kept me in the fold. Then later in the fall, they suggested that they'd finally be coming out with version 2.0 around MacWorld SF, which again has kept me on the string.
Now today I discovered that version 2.0 has been delayed for Leopard, which we know is at least another quarter away, and I'm becoming concerned that their success may have gone a bit to their head and they've been spending their time on stuff other than programming.
They only post to their website's blog every few months, and then only to say 2.0 will be great, so I'm beginning to lose the faith.
All that said, Delicious Library is a great first effort, the interface is gorgeous, adding records is a breeze with barcode scanning, and the program is easy and fun to use. Even if you have to update the individual records manually because the data can't be pulled down from the Internet, the interface is clean and easy to use. If it had a decent way to print reports from the database, I wouldn't care if they ever upgraded it, but exporting records into Excel is not acceptable.
I'm very close to shelving it for awhile, as I tediously continue to update my old FileMaker Pro database. Printouts are necessary not just for ready offline access, but for easily updated insurance records, and I don't care to spend an afternoon exporting and formatting to accomplish that when FileMaker Pro will print the report with the simple execution of a script.