He should be used, it brings more variety to our bowling attack, 2 SLA and then either an erratic leggie like Kapali or Ashaful to go with Aftab.
I'd say use him 2-3 overs Max would be 4 beacuse he's a little expensive.
People say Jaywerdene threw his wicket but still Ash very deciptive and had a few deliveries where he flat out fooled the SL batsmen. He mixes up his deliveries very well legspin,offspin etc.
I think he's more than a patrnership breaker.