I got a Santa Cruz Stigmata about month ago, and so far I love it. I haven't raced it yet, but it feels real stable over rough terrain. It has a low bottom bracket which interested me, but my pedal has hit the ground in some tight turns. I think this is something I can easily adjust to. I have ridden it mostly on the road with road tires. I will certainly have a more detailed review with a few races under my belt in the upcoming months.
As far as geometry, I have the 54 stigmata, but would be a 51 or 52 in Cannondale's lineup. Geometry is a huge thing for me, and a major reason I went with the Stigmata was because I though the geometry was right for me.