LOL, I'm not going to get all touchy about the PT at Stainburn 😎
It was the first one we attempted and it's been through umpteen incarnations and re-builds. If you think it's bad now did you ever see it 2 years ago 😉 It's also a bugger to win good material to build with there so it means rebuilds and tweaks are difficult to do. The finer fraction of the soil / sub soil is great stuff but you don't need to go very deep before you're hitting a lot of rock. That makes digging incredibly hard work. Hence why Clixby's (god bless Hugh) put us in the drainage channels, rather than digging them all by hand.
Honestly though, IMO it's a hard track. I can do laps on it though (and like Nick says there's an "easy" and a "hard" direction). Given I'm no great shakes I'd suggest that if you can't or folks you've seen haven't managed it then they probably aren't "getting it" yet, for whatever reason.
Personally I need all the help I can get with rock hard, fast rolling tyres and a dedicated HT. Trying it on a FS with proper knobblies and trail pressures will make it a lot more challenging.
TBH, I'm happy to admit it's not perfect (nothing we've ever built has been 😉 but we have built, or tried to build stuff. We're aware enough (ish) to know when things haven't worked and to learn lessons from that. Hence I think I/we know a lot about what can go wrong. It doesn't necessarily mean we'll always get it right, but it's a bit of a head start and just leaving people to make the same mistakes would seem daft.
Say Hi next time you're up at the woods if you see me. Old bugger, red estate, poor skills, talks a lot 😎