Thanks everyone. I agree the fold was pretty weak. Given my read of the situation I'm OK with it but I wanted to see what you all would do, even though I expected mostly "i insta-call" responses. I think I just psyched myself out due to the fact that I've lost a lot of money lately with bottom set in multi-way pots where all the money goes in on the flop, and afterwards when I lose I think, "well, duh...".
Results, if anyone's interested: Preflop raiser had AA, so my read was totally wrong on him. UTG called the all-in with
[Ts] and made his flush. I ran the hand through PokerStove and it said I had 54% equity.