As a practical matter, this won't change a thing.
Andrew,
As someone who understands something about the automated processes, conducted by third parties, that generate the vast bulk of DMCA takedown notices, I can tell you that this case is going to be much ado about nothing, despite UMG's grousing to the contrary. They'll just have their copyright monitoring agencies insert some additional boilerplate language into their DMCA notice templates that makes some mention of non-fair use. Even then, the notice will only be called into question if -- as was the case in Lenz -- it is challenged on validity grounds. 99.999% of DMCA notices never reach that stage.