Was going to, then decided to pull out. Rode it in '09 on fixed though. Was a relief to get to Yad Moss and stand up for a bit after 500km of flat. Like Greenbank, ICBA to change ratios on rides.
A forumeanger did it on fixed, on a Langster with baby blue Velocity deep v rear wheel.
Perfectly doable, it's surprisingly less hilly than I expected when I did it in 2013, it's just the usual really steep section every now and then that threw the oversea audaxers off.
Doing it fixed, any souls? The hills are long-ish but not that steep...