Currently, he has an offensive rebounding percentage higher than anyone on the team except Wilcox or Stiemsma. However, his defensive rebounding percentage is lower than those of Rondo, Pietrus, and Daniels. His overall rebounding percentage is slightly better than Jeff Green, somewhat worse than Glen Davis.
He seems unlikely to be more than average as a rebounder, but his other skills are such that he could easily be an above-average player overall even if he is a poor rebounder.