Well, I'm about to move from a Super T to a 66 RC....so I'll explain my motives.
I actually wasn't sold on the whole long-travel single crown thing either. Then, last labor day weekend, I hooked up with an established rider who was riding a 66 on his RMX. I rode about 3 hours with the dude (he was a single and so was I) and I was BARELY able to keep up. But, as a result, I got a lot of time to ask talk to him about the 66 and various other topics.
Yes, he said he was riding it primarily so he could do X-ups that day and was tweaking his airs a bunch / throwing his bike all over the place, but he was saying that he was riding the 66 a ton except for really hairy stuff (e.g. redbull rampage) or for super big hucks. Seeing him ride that day pretty much sold me on the single-crown's capablities. He told me a few of his buddies (Robbie Bourdon, Randy Spangler, etc.) were riding the 66 for pretty much the entire summer and hadn't even switched back to their 888's once. Sure enough, I picked up the latest NWD film this fall and Bourdon is doing huge ladder gaps with the 66.....
I have a Stinky with a Super T and haven't had issues with the turning radius - even on tight switchbacks. At times, I may have to track stand, but whatever. I'm gonna sell my Super T and pick up a 66 in the next couple of weeks and intend to put it on a VP-Free. It will be about a 1 lb. lighter than my Super T, but I'm mainly looking to be able to have more freedom in the air with my bike. FWIW, I plan to run either a King, Race Face or FSA steel headset just to reinforce the headtube a bit more.....
EB