I took my Bfe last year and pre-rode the qualifier on it.
It's perfectly doable, and I *really* enjoyed the lower section below ADH – the new singletrack through the trees had only just been opened and was mint. Drifty, loamy hairpins. Perfect. They were cut to f'ck 3 days later mind…
That said, I was absolfookinlutely knackered by the bottom. Arms were killing me. Thats a 20-30 min run depending on how quick you are. The main race is double+ that. I'd happily ride a hardtail for it, but I absolutely would not want to *race* on it. Whatever your best intentions to "just go along for the craik", once you're on the startline, the goggles are on, the music is blaring and the helicopters are circling overhead, it'll get very serious, very quickly, and you'll probably attempt to ride out of your depth.
In conclusion, if you want to do it, then do it. But get very, very fit, and very, very strong, or be prepared to smoke a fag on the startline after the tapes have lifted, then ride down at your own pace.