one of the problems with the filtering (particularly in genres) is that using more than one filter is next to useless, due to the fact that it will show all results for any title that has one genre match. so "family" & "comedy" will return both finding nemo and also south park. similarly if i have a collection of movies i like and my friend has a collection of movies they like there is no easy way to determine what intersects.
however that is not to say the OR selection is useless either.. For instance, if i want to watch a tolkien movie i can select from the "lord of the rings collection" and "the hobbit" collection and get the combined sum of the two collections.
i'd suggest a toggle switch similar to the "unwatched" switch located at the top of the corresponding filter page (next to "deselect all"). this would not only speed up finding a specific movie (as there is less noise to wade through) but also cut down on the need to utilize subgenres do filter down only what you want.