"The fair use question is a mixed question of fact and law. Reviewing courts should appropriately defer to the jury’s findings of underlying facts, but the ultimate question whether those facts amount to a fair use is a legal question for judges to decide de novo. This approach does not violate the Seventh Amendment’s prohibition on courts reexamining facts tried by a jury, because the ultimate question here is one of law, not fact. The “right of trial by jury” does not include the right to have a jury resolve a fair use defense."

Or to put it another way, convincing a jury that something is or isn't fair use is very different than convincing precedent-bound judges, especially with this on the books as the controlling case.

In final impact, it seems like an incredibly good judgement for everyone: you can prove to a jury what was / wasn't copied, and then a judge will apply a standard fair use test over those facts, with a tendency towards allowing transformative use.

Legal protections against copying, room for progress, and (most importantly!) more certainty and standardization in how cases are decided.