This trek was the best holiday ever! I had such a good time and made some good friends who I am still in contact with! It's an ideal way to see a lot of the States in such a short space of time.
I can't say which place that was my favourite as I enjoyed all of it, well apart from the times when I'd find some creepy crawly in tent! The places I would say were the best for me are, San Francisco, Yosemite NP, New Orleans, Washington DC, New York, Chicago, Yellowstone NP, oh and Niagara Falls!
The tips I would give anyone who wants to do any of the trek are:
Travel light - You will be surprised how much you buy on your travels!
Bring a spare roll mat - They give you one, but 2 makes such a difference!
Travelling in the van when it's hot can really tire you out, so drink loads of water!
Bring plenty of CDs for when you're travelling in the van!