First of all, while I agree it will be crowded and Hollywood Blvd will feel "packed" on 9/13, there is NO WAY the park will hit capacity. We are still talking about mid September here. Everyone on disboards knows about the event and everyone from the boards that will be there will most definitely be excited about attending but believe it or not, we on disboards are an extremely small percentage of the Walt Disney World visitors. The majority of people you see there goes once or twice in their lifetime and those trips usually occur during school vacation - Xmas, Easter, summer. Heck, the crowd calendar still lists 9/13 as a crowd level 1. You can't get any lower than that.
Second, unfortunately, 9/13 is the only day we are there that the party is happening. And we are rarely there during the Sept/Oct time frames - trips with the kids are usually over the summer and our adult only trips are usually in November for F&W, so I'm not sure when we will get a chance to do the party again.
So I'm still considering both. We are staying at the contemporary and could go back after MNSSHP, change, and cab it to DHS to see the fireworks and catch the last hour of the festivities. Thoughts?