The worst thing about Jersey week in WDW is getting airfare from/to PHL, EWR or ACY! If you go on a split week (say Thurs the week before Jersey week to Thurs the week of Jersey week - as I have done in the past) you WILL notice a huge increase in crowds as you get closer to the Thursday and Friday of "The Week." That said, if you are comparing it to March, April or July, you will find it not so bad. If you are comparing it to the week after Labor Day, it will be crowded.
I agree with JohnNJ, that is, IF TGM took the time to update his site. We had his "plans" with us last week, and noticed many errors and discrepancies between reality and his info. It was disappointing. His assessment of the crowds Labor Day weekend was flat out inaccurate.