New toy:
Booxter, a shareware Mac library management tool. Most of it is straightforward, the key things of interest are (1) exports to a variety of open formats, so it doesn't trap your data (2) It can use the iSight (or apparently any firewire camera) as a barcode scanner (it also supports the cuecat and other more normal scanners.)
Pretty good workflow, could use some more defaulting or bulk update operations, but the kind of flow I was going for with
ThokBook (start app, scan-scan-scan, search web for metadata and album covers) is actually there, using LoC and Amazon. Also has a basic "location" and "lent to" interface.