Instant Replay

Pro tennis currently makes the best use of instant replay to review calls. It is fast and infallible. Of course, the nature of tennis makes this possible. Almost all disputed calls are line calls which existing technology handles quite readily. Replay also works reasonably well in reviewing the clock in basketball. It is employed at the end of quarters or halves so there is no halt in the game's progress and it is quite definitive. However, in football, replay infringes on the continuity of the game, and as often as not is not conclusive. I fear the experiment in baseball has a similar downside. Already interminable games will get longer, and many of the reviews will produce ambiguous results at best.