I only do this when there are a LOT of replays available, like for graded stakes. I agree that breaking can be very important, but I just don't have time to watch every horse's past performances for every day races.
OTOH you can have horses who can stand, like they're stunned in the gate, and still come around to win, I seem to remember Zenyatta and a few other horses doing stuff like that.
I've also made $ on horses who keep breaking badly, and then finally get it right and win at high odds. My feeling is that the stumblers and air-jumpers may eventually get a good break and their odds will reflect only their past troubles.