Easter week 2009 (which also was the first full week of April) was crazy crowded. Early afternoon wait times in Epcot were over over 2+ hours for Soarin', Test Track and Mission Space. (We just laughed...nothing is worth that kind of wait!) The Magic Kindgom was closed due to capacity limits three days that week (resort guests arriving on Disney transport were admitted.)
Easter week 2010 (still the first week of April, but Easter was the first Sunday rather than the second) wasn't as crowded as previous year but was still VERY BUSY. Many southern school systems always have the first week of April off for spring break, so when Easter falls during that time (when other schools are out for Easter) the parks will be full.
Bottom line...get an early start each day and utilize fastpass. And if you are mentally prepared for large crowds and are patient, you will enjoy your vacation more.