Never sailed with Challenge, but I've spent a lot of time working on the 67ft Challenge boats. They're awesome, particularly if there's a lot of wind - have been in F8+ at 20 odd knots, with most of the canvas still up. It's some of the most exciting and rewarding sailing I've ever done.
The boats are definitely designed to be sailed by a 'team' - there's no room for individual glory. There's little in the way of labour-saving devices. Everything is extremely heavy, and the loads on the sheets are unbelievable. Hoisting the main takes 5 or 6 people hauling the halyard along the foredeck. Speaking of the foredeck, nothing furls, so sail changes in big seas are common, and very wet affairs. Don't volunteer to weigh anchor /forums/images/graemlins/smile.gif
You'll come back bruised and battered, but with a huge smile on your face and a few new friends - It's hard not to get to know your fellow crew.