How strong is OKC's bench?

If this is the year Oklahoma City wins it all, a number of things will have to go right. Certainly, their big three of Kevin Durant, Serge Ibaka and Russell Westbrook will have to be healthy for much of the season and throughout the playoffs. Players like Thabo Sefolosha and Jeremy Lamb will have to step up to fill the scoring and shooting void left by Kevin Martin. The play at center will have to improve. And the bench has to prove it can be counted on whenever the stars need a break. Just how good is OKC's bench, anyways?