I have done BCBR four times in the past five years. Three of those were on a Scott Spark (the 120mm version). It's been an excellent bike for putting in the miles on rocky terrain and racing stuff like BCBR. No issues whatsoever. The Twinloc thing can be polarizing. I actually plotted to remove it before getting the bike... Now I'm totally sold on it. For marathon racing (or BCBR) I really like being able to control the suspension over the really varied terrain. BCBR has a lot of singletrack, to be sure, but you sometimes have to grind it out on fire roads to get up there.
The technical difficulty of BCBR is definitely subjective. Some people, who ride/race on tame terrain are blown away by it. Others, who, say, live in BC to begin with, will notice that the race uses plenty of "blue trails" and avoids the truly gnarly stuff the area is known for. It is an XC race, afterall. I ride/race XC mostly in Quebec Canada and, while the race was certainly challenging in every way, it wasn't scary or beyond my capabilities. Fantastic event with loads and loads of wonderful singletrack in a beautiful part of the world.
The bikes around me in the race (top 50ish) are usually "modern" "progressive" XC race bikes -- dropper post, 100/120mm travel, slackish, 2.35 tires with some durability and bite. Seems like every manufacturer is making one now.