As it seems is always the case, as soon as I published the WIA library, I found some problems.  The original library worked fine in the test application, but as soon as I moved it into a larger-scale application that does a lot of wacky multi-threading, multi-AppDomain and reflection calls I started to see bad behavior.  It all worked fine if you kept the original list of cameras, but if you added or removed them they started shifting around or existing cameras no longer worked.  So I've debugged and reworked it a bit and the new version appears to be much more stable and friendly in a production environment. 

Download the code at the original blog entry.