The band visited WDW from 4/1 - 4/5 and my husband was a chaperone. He said he was very surprised at the number of people in the parks. With the exception of MK on Thursday and AK on Saturday--they walked on everything. By contrast, they were "shut out" of Typhoon Lagoon on Friday because it was jammed by noon--not surprised by that though given the hot weather of late.
He did say that he felt crowds were increasing by the weekend, but didn't know if it was due to spring break or merely because it was the weekend. They stayed at ASMu and it wasn't full either.
BTW, he just read in the Wall Street Journal that attendance is predicted to be off about 45% this summer. We noticed that crowds in June last summer were less than normal--guess we'll be appreciating that decrease this summer too--provided predictions are accurate.
I will be curious to see how crowded the Easter season/spring break (late) will be.