Hmm that is certainly some admirable driving. However, speaking as someone who once was in training for single seater racing until I realised I simply could not afford it, it actually isn't that difficult. A large part of precision lies in the vehicle itself, in how well it is able to precisely translate driver input into the desired output, as well as send the needed feedback that allows the driver to be precise.
As part of the attempt to begin a racing career, I raced professional sprinter karts, and karts are very very precise things, even at high speeds. We regularly topped out near 100mph on our pro-karts on a twisty tight circuit about half a mile long back home, and they weren't even shifters, but used a single sprocket with a fixed drive ratio. The precision of control on these things were phenomenal AND adjustable. Part of the track was a long 180 degree double apex curve, and we used to drift around it for fun. It was not difficult at all to shift the angle of slip when we were drifting for fun, and clip both apexes very cleanly and precisely plus have the rear outside wheel clip the entry and exit curbs cleanly as well.
These karts were so precise that we often practiced saloming between cones spaced closer to each other than the kart was long. Given that they're about as wide as they're long, it does mean you have to go thru the gap at 90 degrees to the line of cones, turn it pivoting on the inside front wheel by oversteer, and then do the same again, with millimetre precision. Granted, you'd still have to be decent enough a driver, but it was doable. What Ken Block is doing there, is impressive to most outsiders, but to anyone who's been lucky enough to be involved in motorsports proper in some form, the insider knowledge plays a huge part. Not to mention Mr Block has a nice huge empty area to play with, where most of the tricks requiring more ludicris slip angles in areas with plastic barriers defining the boundary rather than more painful things to crash into. There was one corner where I felt a tree's position was worth some mild concern, but that's about it. Sadly Mr Block doesn't seem to do as well competing against other drivers when the scenary is beyond his control.
For truly impressive driving displays, where it isn't just enough for the vehicle to be a precise and compliant tool in one's hands, check this out:
Patrick Snijers at the '88 Manx Rally
http://www.youtube.com/watch?v=ZJB8BtkSEHM
No doubt having a compliant, precise machine helps, but still takes some real guts and skills to do that on a narrow twisty road. Not to mention Mr Block has the benefit of a SWB 4WD factory-backed machine, while Mr Snijers was in a RWD M3 that was independently prepared by Prodrive without any factory backing from BMW at the time(BMW did not want to get involved with rallying and was focusing purely on touring cars).
On another note, I don't quite think you'd be able to do all of that with your GT500, on the simple fact that a lot of what he's able to do is due to the fact that his WRC fiesta has 4WD. The last bit where he spins the car with the axis through the dead center of the car itself, that is a purely 4WD trait, I have never, ever seen a RWD car or FWD car pull that one off.
