I raised $50 more, to $100 total. He folded, I win $172 pot.
Hand analysis:
What does Villain have?
Pre-flop limp suggests virtually any two cards. Its not uncommon in a 6-seat game to limp with a huge range of hands.
Villain’s flop bet suggests that he got a piece of it, and is looking to chase away a flush draw, or a goofy straight draw. He might have A9-A2, or a wide range of hands with an 8 or 6. AK-AT probably would have been a raise pre-flop, so I don’t think he has these hands.
Villain’s turn bet suggests that he thinks that I am on a draw, based on my call on the flop, and he is again trying to drive out my draw. He now probably does not have A6, or he would have checked and let me dig my own hole. He might have a 6, but this is unlikely. He probably has Ax or an 8. He also might be bluffing with junk or on a flush draw himself.
River bet is revealing. My guess is that he no longer thinks that he has the best hand, or he would have bet at least the pot or more. If he had a monster (A6 or 86) and really wanted a call with a strong hand, he probably would have bet smaller. He might be afraid that I was not on a draw, but maybe hit a lucky boat, or have A8. On the river, I assign this range of hands and probability of that hand:
Ax, lower than A8 – 50% (results in chopped pot)
AT, A9 – 20% (I’m beat)
8x – 20% (I win)
Flush draw or junk? -- 10% (I win)
My play:
His range of hands, combined with his river bet, suggests that he’s susceptible to folding to a raise. Facing a raise with any of the hands that I think he has would be tough to call, if Villain assigns 50% of more probability that I have the winner. Villain is also a decent player, so he’s not just going to auto-call a raise like a weaker player with any pair. (Interesting how the thinking players are more likely to be bluffed.)
From his perspective, if I had A6, 88 or 86, for example, I would have played the hand exactly as I did, and then raise on the river. I might do this with A8, also. If I’m Villain, my weak ace on the river shrivels up. A mini-raise on the river also has the benefit of losing the least if he calls, plus it looks like I’m just begging for a call. Finally, my guess at his hand ranges means only 20% chance that I’m beat. I might be wrong, but that’s poker.
Raise it up!
Footnote for Yeltsin: Why was I just calling on the flop and turn?
Sometimes calling is the right move. Flop bet was worthy of a call, since his range of hands on the flop looks something like this:
Ax (not A2) – 50% (I’m beat)
8x or 6x – 25% (I’m ahead)
Draw – 15% (I’m ahead)
Pure bluff – 10% (I’m ahead)
At a 6-seat table, players bet with weaker hands on the flop, like just a pair eights, partly to test the waters and partly because eights may be the best hand.
On the turn, my assessment of his range hands is the same as discussed above:
Ax, lower than A8 – 50% (results in chopped pot)
AT, A9, A8, 6x – 20% (I’m beat)
8x – 20% (I win)
Flush draw or junk? -- 10% (I win)
AK, AQ, AJ – 0% (he very likely would have raised pre-flop with these hands)
Worthy of at least a call. Plus maybe I can now set him up for a bluff on the river (or simply a raise with the winner). Sometimes, calling works.
or 
. He never slow played, so he was trying to take the pot down. His bets equalled the pot up until the river where he backed down and didn't try hard to convince he hit his hand.
Linear Mode
