I did in '06. You can take a duffel bag that is large enough to hold everything you need unless you are bringing a tent the size of Grand Central Terminal and a different off-bike outfit for each day. I brought a medium sized 2P tent, ThermaRest, sleeping bag, maybe five sets of riding clothes, a couple of sets of off bike clothes, towel, etc. I probably had a flat pillow, too.
Definitely don't abuse the staff. It's minimal commpared to something like Cycle Oregon, which I have done three times. There were no "sherpas," so you had to carry you own bag to the truck where there were one or two helpers who would assist with loading. You also had to carry your own bag to wherever you wanted to pitch your tent. Definitely use a dry bag or put your stuff in a garbage bag inside your duffel. The penultimate day it rained cats and dogs. The luggage was placed under a giant tarp, but people moved the tarp while searching for their bags and didn't bother to make sure they hadn't left bags on the fringes uncovered. Also, the people who unloaded the luggage managed to find the lowest spot of ground at the bottom of a ski lift. I saw some bags with pools of water on top and others sitting in inches of water.
If the last few years signify a trend, I would be prepared for rain, either on the road or in camp. I have spoken with several people who have done it recently. They experienced a good deal of rain.
Lunch is on your own. I generally didn't stop for lunch but rather just had snacks at the rest stops and my own Gu and Cliff Bars. It was warm the year I did it so I wanted to get off the road early. I usually bought lunch in the finishing towns. I liked the wine carrying feature. You could stop at selected vinyards and buy wine. A van would cruise by and pick up and transport purchases until the end of the tour. Or if you happen to see a SAG van hanging out in a town where there is a wine store, you can buy a couple of bottles and leave it with the driver.
The last night they threw a big kegger with catered BBQ.
Depending on the route, there definitely can be some extremely steep grades going W-E. There was one hill that many people walked at least part of. A 24x34 should do the trick.