I am your sword... I am your Shield...
It is really good for avoiding power weapons and splatters. Banshee bombs and wraith mortars are rendered useless against a very good evader. Although I do not think it is over-powered because you take damage if you roll into things. Another downside is that you cant cancel mid-roll, and you cannot attack during or right after the roll. I use it on invasion and btb, but i think it is not that effective in other game-types.