  We theoretically study the superfluidity properties of a non-equilibrium
Bose-Einstein condensate of exciton-polaritons in a semiconductor microcavity.
The dynamics of the condensate is described at mean-field level in terms of a
modified Complex Ginzburg Landau equation. A generalized Landau criterion is
formulated which estimates the onset of the drag force on a small moving
defect. Metastability of supercurrents in multiply connected geometries
persists up to higher flow speeds.
