Virtual Routing - vMX, CSR, Vyatta, etc

Is anyone doing x86 routing in production? What are your thoughts? Had any problems? Is there a x86 routing platform that I've missed?

Is it cost effective vs buying hardware (Including server costs)? Are there any latency implications?

I've been looking into doing this for terminating customer circuits, both IP, PPP and MPLS/VPLS, I'm interested if it's worth the effort / cost of setting up a couple of servers with KVM and licensing some copies of the above to same some RU space.