We went to MK and Epcot for the day last Saturday - crowd calendar had it at a 4. The lines for the FP+ kiosks were longer than the majority of the lines for the rides. We didn't even bother using FP+ since it was truly just a lazy stroll to ride some rides and eat some food, although we would have benefited from it for the "big ones."
I can imagine that during the last week in March, using the FP+ is going to be necessary, and I suspect the lines at the kiosks are going to be seriously long. (The same crowd calendar has the last week of March as 8 and 9.) All I can say is get there early and get those FP+ lined up ASAP, because I don't suspect the lines at the kiosks will get any shorter as the day goes on!