If this is upheld by the SCOTUS, the use of recess appointments to temporarily get people such as John Bolton into office is now dead (unless you can persuade current officeholders to wait for recess.)
Much as I liked Bolton, I think it's actually a good thing.
The Court was asked to consider whether or not the senate was in recess, and whether or not the appointment was within the recess appointments clause. From the tenor of the opinion, I think that plaintiff argued that "the recess" is associated with adjournment sine die, and that the words "vacancy happens during the recess" mean what they say. Not all vacancies are amenable to recess appointment, under the constitution. Just saying, the result is one that the court was asked to consider.
If upheld (and I don't trust SCOTUS to follow the constitution), this decision lights a bit of a fire under the senate. It has been shirking its constitutional duty for decades. All it has to do is reject, by vote, those nominees that it objects to.