Yes, hate to pile on, but I've done it 3 times. For some reason I get the itch every 5 years to see if it's as bad as I remember it being. And it always is. Such a boring course with limited and low quality true singletrack compared to the choices in Squamish these days.
Certainly a lightweight XC FS bike would be best just for your back over the longer duration. But a pinner hardtail would be fine.
Last time I did it (3 years ago?), I come into the Plunge, immediately pass 3 people who never even started riding it. They turned onto the Plunge and shouldered their bikes. Then, 2nd switchback, there's a guy dabbing slowly around a corner, I go to pass on the inside and he yells at me to slow down and be careful because I'm going to make him drop his carbon bike. It was ridiculous. I'm not Stevie Smith, but I think I passed about 15 people of that short section of trail. Some friendly about it, others quite grumpy.
What is nice about the race is the conversations you strike up over the course, especially up 5 mile as you slowly spin by people. Lots of good people out there.
What is especially bad, is Jack's trail where people just bog up and you're stuck for WAY too long. Hammer out of the gate and up the road just to minimise the road bikers in front of you when you hit singletrack and the dab-a-thon begins to unfold before you.