I have an 01 Jamis Dakar Expert with (I think) a Fox Vanilla R rear shock. It's a coil spring unit, which I run most of the way to full preload. Given how old the shock is (time-wise, not usage-wise) I'm thinking there's something better on the market from a performance perspective.
I do mainly cross-country riding. Lots of twisty single-track, with lots of climbs. No jumps, no drops, nothing like that. I'm thinking an air-sprung unit might be better.