We've flown that route probably a half dozen times since they started it (about two years ago, I think) and have never had any issues with delays or luggage. (And prices have come down now that they offer several flights a day, yay!). That said, I have not checked the overall reliability on flight aware. We fly from the west coast and the AA MIA-EIS route is definitely our preferred....fewer segments, less complicated, less travel time, and fewer variables to foul things up when compared the the STT or SJU routes.