After playing with it a little it can sort of get me where I want. It's good that they're dynamic - rather like autoplaylists in a music app like foobar or similar. But in order to get what I want to get, I would have to have a huge list of custom filters, all with prefixes to sort them properly (2D Platform - Super Mario Bros, or Text Adventure - Infocom). To go further would be even more complicated - finding all handheld Super Mario Bros. games from 4th gen systems, or finding all Zork games and arranging them in the main window by release year for example.
Multi-level filtering is much cleaner (select "Text Adventure" in the first filter (genre), "Infocom" in the second (publisher), then "Zork" in the third (series)).
I think it would be particularly important if, as I've seen implied here in the forums, LB eventually expands to fully support other media.
Think iTunes...