At first I thought Philly would be your race of choice...considering you have good luck racing in that city :) But I bet the timing was not optimal...correct? (meaning if all goes well, only a week or 2 of downtime before training again!)
Two reasons really: 1) I don't want to put all my eggs in one basket. This way if for some reason things are together for Steamtown, I still could do Philly. 2) Recovery time. I probably would start training for Boston sometime around January. Ideally I'd like to have a good 3-4 weeks of downtime before starting back up again.
I love that you are planning ahead! It's the only way to go!
This might be a dumb question, but couldn't you qualify for Boston in the fall of 07 and run Boston the following year? if you didn't want to run 2 marathons so close together? Just a question. But it looks like you want Boston 2008! And I think you certainly did your research.