Acceptable slow play with flopped set?

[autonic]

Full Tilt Poker - No Limit Hold'em Cash Game - $0.10/$0.25 Blinds - 5 Players - (LegoPoker Hand History Converter)

SB: $35.25
Hero (BB): $25.00
UTG: $20.10
CO: $26.65
BTN: $30.65

Preflop: Hero is dealt J[img]/images/graemlins/club.gif[/img] J[img]/images/graemlins/spade.gif[/img] (5 Players)
UTG folds, CO calls $0.25, 2 folds, <font color="red">Hero raises to $0.85</font>, CO calls $0.60

Flop: ($1.80) 5[img]/images/graemlins/club.gif[/img] 9[img]/images/graemlins/spade.gif[/img] J[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">Hero bets $1.25</font>, CO calls $1.25

Turn: ($4.30) A[img]/images/graemlins/spade.gif[/img] (2 Players)
Hero checks, <font color="red">CO bets $3.00</font>, Hero calls $3.00

River: ($10.30) K[img]/images/graemlins/club.gif[/img] (2 Players)
<font color="red">Hero bets $5.50</font>, <font color="red">CO raises all-in to $21.55</font>, Hero calls all-in for $14.40
Uncalled bet of $0.00 returned to CO

Pot Size: $50.10 ($2.50 Rake)