I seem to recall a discussion a few days back where someone said that "smart" didn't route to the AMEX. I had it happen today. The execution took about 15 seconds and I thought it wasn't going to happen at all. Surprised to see the order go to AMEX.
Well actually it was a surprising circumstance. All of a sudden a bid was posted @ 12.30 while the market had been 12.00x12.40 for quite a while and the underlying was falling. So, I hit it and figured, after the time elapse, that it wasn't going to fill. It did and the new bid dropped to 11.80. Go figure.