Well i played few weeks as Concealment, and now switched to Lethality. Now i am getting much more fun then with stab-stab-cloak-stab-stab Consealment. Nothing interesting in 3-4 shot everyone. Lethality is much harder to play, and if you just want to rollface peoples around - stick to Consealment. But if you like a chaleging and fun speciality, then lethality may shine in your hands.
GL.