I attempted half-marathon only. After about 12 - 15 km my knee decided to give up so after that I half-run / half jogged. Not fun anymore. But first 15 km was a breeze. I did not practice and prepare for this even at all. No special training, no long-distance runs (my preferred distance is 5 km), nothing. And if it wasn't for knee failure I'd have done it in pretty good time. I was really enjoying the run, not really fighting with any fatigue, not fighting with heat. Pure joy of running. Seriously!
It's not 2800 m above sea level (as advertised), it actually is about 1700 (same as Nairobi). Hot? C'mon, the same weather as in Nairobi. So all that hype about toughest maraton on earth is much, much over-stated. Whoever went running in Nairobi is prepared for whatever he's to face in Lewa. I did run sometimes during mid-day sun in Nairobi and was more tired after 5 km than I was after 21.4 km at Lewa.
Additionally there are water points every 2.5 km where they give you water, wet sponges (to help u style your hair, or what), lucozade and fresh orange (in nicely cut quarters). Tough? Phew, come here to Aikido classes in mid-summer heat - this happens (at times) to be tough...
So the question - am I good? Well, perhaps I am. But the point is - half marathon is a walk in the park. If this is one of the toughest ones - go for it, guys. The atmosphere of all the runners is great, people supporting each other, really nice social experience.
An interesting thing - in toilets there was no lavatory paper but there were whole crates of condoms... You know - only in Kenya ;-)