I've made the trip 5 or 6 times and it's more than worth the effort to get there. I trailer my car in from Oregon and make the 1300 miles in two days (three if I want to loligag).
Al does a fantastic job putting the cruise together and I'm a strong advocate of making the Colorado trip part of your bucket list. Spectacular scenery and a really great bunch of people.
Don't forget to bring a camera and spare batteries.
Here's a link to some photos from last year's run.
Cruise Colorado 2011 Trip Report - FFCars.com : Factory Five Racing Discussion Forum
DonC