With as far south as your coming from I'd consider taking I-81 up and avoiding the DC/Baltimore area. You can actually follow 81 all the way to I-84 in Pennsylvania. Then 84 past Newburgh NY as above through CT into Mass. to 90.
You'll miss lots of urban congestion, tolls, traffic and headaches. The few extra miles are, IMHO, worth it. Traffic in the BC to NYC corridor can be horrendous not to mention those tolls really add up.
I've never taken our rig on the GSP, but I'm told those few low bridges are low - to stay in the center lane for them.
Happy Trails!
