Of all of the times of year to go, spring break -- and Easter week in particular -- would be my last choice.
Setting aside the sheer attendance numbers, spring is also a logistics challenge. During the summer, the parks can be staffed up as much as Disney wants (up to a certain capacity). There's a full roster of local college CMs who are available to work. Spring break is surrounded by much quieter periods, so you can't recruit as many seasonal CMs, and local college students have varying spring breaks. This puts an enormous pressure/strain on existing CMs who must put in longer hours with less flexibility.
Not saying you can't have a good time... and happy that many people report that they are... but if people are asking me whether they should go during spring, summer, or winter school breaks, I'd pick spring last.