I don't have many regrets. I regret mistakes, particularly those that damage other people, and we've all made some of those. But I'm not sad about change.
People in Philadelphia are a world apart from New York. They're very different from people in the New York scene. The New York scene wants your visibility and wants your money.
Proprietary stock-index arbitrage is but one aspect of program trading. Arbitrage will take place whenever there is an imbalance created in one or more markets that are similar.