Interesting river decision

[Blindcurve]

This is a hand from an $11 3 table at PS. BB has been laggy, calling raises in and out of position. He has bet me off of two pots I thought I had impetus in.

PokerStars No-Limit Hold'em Tourney, Big Blind is t200 (7 handed) converter

saw flop|<font color="#C00000">saw showdown</font>

SB (t1904)
<font color="#C00000">BB (t16230)</font>
UTG (t1256)
MP1 (t4115)
MP2 (t4376)
<font color="#C00000">Hero (t6929)</font>
Button (t5690)

Preflop: Hero is CO with A[img]/images/graemlins/heart.gif[/img], 4[img]/images/graemlins/heart.gif[/img].
<font color="#666666">2 folds</font>, MP2 calls t200, Hero calls t200, Button calls t200, <font color="#666666">1 fold</font>, BB checks.

Flop: (t950) A[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/club.gif[/img], Q[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">BB bets t400</font>, MP2 folds, Hero calls t400, Button folds.

Turn: (t1750) 8[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">BB bets t600</font>, <font color="#CC3333">Hero raises to t1800</font>, BB calls t1200.

River: (t5350) 9[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">BB bets t2805</font>

Critique on the play so far, and what do you do on the river?

-D.