I agree with all sides of this, just want to remind people to keep in mind that funding does not necessarily come with an acceptance. I had gotten two acceptances, but for one I didn't hear about my funding until two weeks later, and for the second I also waited a few weeks later to see if I could be considered for a TA. Certainly once I got that information I didn't hold onto both, but until then there was not really much I can do.
That being said, once people have all the information, they should (as I was told) decline the less optimal school (or at least less optimal by their opinion). Then, as another offer comes in, they should repeat this process so they never have more than two complete offers at a time.
Good luck to all that are waitlisted and good luck to all that have received acceptances... Both of these things are great news!