Speaking of which, how does IDImager compare with IMatch (and others) in the context of cataloging and searching very large image collections?
It's a few years since I gave IMatch a thorough trial, so I might be a bit out of date - though, on a quick glance, the program doesn't seem to have changed massively since then.
IMatch is more purely an image catalog program. IDI is an image catalog program with more extra functions that you might want to use if you are using your image catalog.
There is some difference in functions. When I was looking at it, IMatch didn't have a good ability to manage versions and this had been a frequent request and had been in development for some time with nothing emerging/ (not sure if it does now); this was a feature I wanted and so that relatively small point was one of the things that steered me away.
The biggest difference is probably in style. The UI works differently. IMatch is much more of a programmers program (the scripting forum currently has 8905 posts, the 2nd biggest on the board to the General Discussion with 12766; IDI has 2150 posts in its scripting forum, with 13042 in Product Related and 9962 in IDI Pro (and 7986 in Bugs & Problems; IMatch doesn't have a forum for Bugs).
It's a question of what suits you best. They can both handle large databases of large images very well.