Media Folders Instead of Genre?

[AgileHumor 123]

So I think the writing is on the wall that Genre is a better way to segment media than the traditional media folder/collection.  This is due to most apps not supporting media folders...or not supporting it well.

 

First, is Genre the way to go for media nirvana?

 

Second, the big issue for me is adding the metadata in a bulk fashion.  For example, for my current Christmas media folder/collection, I'd like to make these 50 movies only have the Genre "Christmas" (remove all others).   I've already tried adding a Genre to the root collection "Christmas" (same place you would refresh all movie data for a collection), but that did not trickle down to the movies. What would be the easiest way to accomplish this task with the least administrative effort?