I've toured on a Friday - a Pocket Gnu. Now, I am not referring to a solo circumnavigation of Siberia or anything like that, just some self-contained travel here in the States. Anyway...
>How was it in general...>
Just fine. The frame is strong and is a very good load hauler. Also, the custom fitting makes for a comfortable ride. The step-thru nature of the frame allows for quick mounts and dis-mounts. All of the usual braze-on's are available as well - racks, fenders, bottle cages, etc. Bike Friday offers its own cromoly pannier racks which work quite well.
Compromises? Well, the small tires don't last as long. I got better mileage from my old 700c tourer. Also, the folding frame does require more maintenance - hinges, hinge pins, quick release levers, longer cable runs and so forth. I keep a clean film of lithium grease on all of the folding bits. The extra-long steering mast might put a bit more stress on the headset. I opted for a Chris King.
>Did you have the 3x9 gearing...>
I've been using the DualDrive hub since day one. It has always worked just fine. My Pocket Gnu has a gear range of approx. 19-105 inches. If I were planning to tour in the more remote parts of the globe, I might consider a standard deraillur setup.
>Did you tow a trailer...>
Nope - panniers.
Overall, I find the Friday to be a fine touring bike. Only you can decide if the folding nature of it - is worth the cost and the compromises.