Get it in w/ underpair or not?

[Laetus]

Villain seems to be a pretty loose and aggressive donk, but I haven't seen him showdown a hand yet. Standard to get it in? Or standard to fold? If you fold 88, which is the weakest hand you get it in w/?

EverestPoker Game #2117902661: Table Nassau-7 - $3.00/$6.00 - No Limit Hold'em - 21:15:11 - 2007/09/23
Seat 1: HERO ($569.60)
Seat 2: trovi99 ($567.00)
Seat 3: morpheo ($603.00)
Seat 4: patcanada ($335.40)
morpheo posts the small blind of $3.00
patcanada posts the big blind of $6.00
The button is in seat #2
*** HOLE CARDS ***
Dealt to HERO[8d 8s]
HERO raises to $21.00
trovi99 folds
morpheo folds
patcanada calls $15.00
*** FLOP *** [6 [img]/images/graemlins/club.gif[/img] K [img]/images/graemlins/club.gif[/img] K [img]/images/graemlins/spade.gif[/img]]
patcanada checks
HERO bets $30.00
patcanada raises to $135.00
HERO ?