Well, I expect that the biblio records will be getting updated frequently, and since I also plan to use virtual shelves (lists) and have members using tagging, item-level item-types seem the way to go rather than duplicate biblios, right?
It's really just the frequency of updates that is an issue. Having item-level item types or not doesn't much affect lists and tagging.
Plus (correct me if I'm wrong) this eliminates my having to choose for Advanced Search - only Collection Code will be available for that?
You can choose whether Advanced Search uses collection code or item type either way, if I'm not mistaken.
Back to icons then, is there a good biblio-level field to indicate in the search results (ideally with an icon) that a given biblio has available (child items with) format A only, or formats A+B or A+C? Fortunately there aren't that many possible combinations. . .
In terms of search results, there is no good way to indicate multiple formats if you're using item-level information. It's a common complaint and we don't have a good solution. The best you can get is to turn on XSLT and see a biblio-level material type (book, audio, etc). -- Owen -- Web Developer Athens County Public Libraries http://www.myacpl.org