This was the first organized ride I ever did. I had an absolute blast. Still the best ride I've been on. Might be partially due to it being my first ride of this ilk.
Well organized, lots of great rest stops. Pretty scenery. If you do the short route, think about riding down and taking the Ferry both ways. We (me and a woman I met on the ride) did this, there were only 6 people on the ferry going over to pick everyone else up, and it was a nice relaxing afternoon. We also had the massage folks all to ourselves.
I was told by the folks that did the intermediate ride that the highway portion was scary, especially in Idaho, but the trail was beautiful. I've ridden the Coeur d'Alene trail a few times since then and it's a great trail.
I'm not sure why, but of all the rides I've ever done, this also had the friendliest riders, I was always in a group of friendly people to chat with.