It really depends on when Easter falls.
Each year our school has spring break the first full week of April. This year will be our 3rd consecutive Disney spring break.
The trips which have coincided with Easter have been a real zoo - but the advantage is the parks, especially MK, have extended hours. I believe the week before is slightly less packed than the week after Easter Sunday.
It is busy but not intolerable when Easter is not within a week either side of your trip. I'm hoping our visit this year (April 2 - 8) will not be too bad since Easter is March 27.