Depends which market. They're used on IBM's Blue Gene, in Sandia Labs supercomputer centre, Los Alamos Super computer centre, at NASA JPL, ran the lighting at Sydney Olympics, are used in Lucent's mobile phones masts.
Vita Nuova is now just one guy, Charles, but I know he makes a living himself working on/consulting for the systems I mentioned. His colleague Rog Peppe, now works for Canonical doing Go.
As I mentioned, Plan9 is used on a few super computer systems for IBM and the DoD.