I've been running in a pair of XA Pro 3-D's and I love them. They're very low to the ground and perform excellent on trails. (These and taping have eased my worries about ankle sprains)
However, the forefoot cushioning is a little light and I'm concerned about an upcoming 50k. Has anyone tried the Salomon XT Wings? They appear to have more forefoot cushioning, but also look higher in the heel, which concerns me. Maybe I'll get a new pair of Pro 3-D's before the race and be done with it.