We rode two sets of bikes:
First I rode the Trek EX 9 carbon full suspension bike. We rode up, up, up, then down a familiar section of trail to the parking lot. I had to keep reminding myself to sit down over the bumps. This bike was like a couch compared to my fully rigid RIG. I sat much more upright--the distance from the seat to the handelbars was much shorter than my bike. It was fine. I climbed the whole thing, didn't fall, and remembered to sit down more. I knicked a tree with the left side of the handelbar on the way down and was thankful that I only knicked it.
Then I rode the Gary Fisher HI FI 29er. This bike was WAY more comfortable. I think that I was stretched out a little more. I immediately said that I could breathe better. It was more like my bike--less squishy. We rode up a rocky section then went down a swoopy area. Usually on the downhill area my legs get tired from hovering over the seat. I sat down more again through this section and my legs felt much better. We crossed McClellon and rode through one of my favorite sections of trail then back to the parking lot.
I think the HI FI is much more of a cross country style bike--which is what I'm more familiar with than the EX 9. Would I ride a HI FI? Sure. Do I need a HI FI? No. I like my bike.
He rode something Trek and then rode a ROSCOE. On the drive home he said that the reason he didn't want to go was because he didn't want to think about a bike other than the one he is riding. He was thinking about the ROSCOE.