The obvious concern, as stated, is the UTG. With Hero's 3-bet preflop, UTG is laid 6.5 to 1 on his call--making a call with a range of A8/K8/78/89/8T appropriate. He will obviously not fold to a capped bet. The UTG check in the first round preflop indicates he probably doesn't have TT, the second nut we would worry about later in the hand.

The CO is insignificant as he gets his last 3/10th BB in on the flop. The UTG check 3-bet indicates he has at least an eight.

The nine on the turn gives Hero the second nut, worthy of capping. This street was played properly.

The eight on the river (this MUST be Party Poker, lol) is the worst card in the deck for Hero. The river call is entirely appropriate given the preflop range which has become more defined on the turn.