I was there for almost a week starting March 19. It was plenty busy, but nothing horrible. I did run into a very busy day at Magic Kingdom that wasn't projected to be especially busy, but I suspect that was because the previous day, which was supposed to be busy at MK, was rainy for the early part of it. I did see a 120 minute wait at 7DMT.
I would agree that you should try to avoid the week before and after Easter, if you can. I think its late March next year. Those two weeks you'll have pretty consistent 9 and 10 level crowds every day.
If you do your homework and book your FP+'s (I was able to get everything I wanted about 30 days out), you'll have a good trip. And the weather is usually really nice!