The interface isn’t for everyone, but I’m willing to put up with it’s complexity to take advantage of the power that it offers.

Depending on how complex you want to get with your categorization, Photoshop Album is a decent product too - it just doesn’t allow as deep a categorization (I think it only allows you to categorize one level deep, while IMatch lets you build a tree structure of categories.) There’s a free download for it too though, so you can check them both out, and decide for yourself.