I rode two weekends last year on my specialized stumpjumper 29er FSR which is a 4"/4" cross country bike. I don't remember the trail names but the two blue trails were easy to ride on this bike, no real challenge. Both black trails were way too challenging, I rode both trails a couple of times but found spots in each that were too steep for me to ride comfortably so I had to walk a number of sections. It gets very very steep in some spots for more of a cross country style bike. For reference, I ride everything at M-hill and south of heaven on this bike. My head angle is ~71? which is the problem. If it was a bit more slack at like 65? I would be a lot more comfortable (rode a friend's Nomad down GRP Load once which had a slacker head angle of ~64? and had no trouble with the steep sections).
Also, tires were super important. The first weekend I went out I had a pair of panaracer rampage 29er's @ 2.4" on which didn't have enough grip (too hard of a rubber compound). Second weekend I went out with Kenda Nevegals and had a much better time.
Lastly, I had the best time coming down the blue trails to where they intercept Ace of Spades, which was a black trail, and then switching to that trail. At that point you're past the super steep sections and just go through some fun rolling stuff with some jumps/drops. Not sure if there is anything new up there this year. Perhaps someone more knowledgeable could chime in?