Hey Mark, to answer ur q - I really like Headshoks. This one could probably do with a service, it seems a little raspy/springy, but it holds air, soaks up bumps and the lockout works perfectly.
For hardcore rock gardens forget it, not enough travel (80mm?) but for XC/general use I think they rule. It tracks perfectly, no fore and aft play at all, and the novelty of locking out fully rigid at the turn of the dial on top of stem is something I came to appreciate v quickly. I now expect it, which put me in a quandary about moving back to twin stanchion forks. I may be selling this bike on soon, but must admit am now a fan of Headshok and CAAD mtb frames. They're just lighter, stiffer and more convenient than other forks of the same travel.
My mate has an F4000 with Fatty Ultras, and they are plush too, and even lighter.
I agree with a reviewer's comments on MTBR -
produce this fork with 105mm travel, and it will be ONE LEGENDARY FORK- bar none. With a quarter-turn lockout, climbs will put all your friends in the dust.
"Every time I see an adult on a bicycle, I no longer despair for the future of the human race" - H.G. Wells
"When I was a kid, if you saw an adult on a bicycle they either (A) stole it, (B) were drunk, or (C) had lost their driving license, or (D) A, B and C" - Malvern Rider