I went last April for Dapper Day weekend, and I was pleased that the crowds were quite manageable - not terrible at all. You have to be smart and use your time and FP wisely, but you'd do that anyway, right? I'd go again for spring Dapper Day weekend. On the other hand, I would never go again any time between Thanksgiving and New Year's. The holiday season was madness and misery last time I visited in December.