I did a small trial of API's Quick Start product, and it didn't do anything. The only factor that might have had effect are that the pH is very high, 8.4, as it's going to be a african cichlid tank.
What worries me most about using these bacteria in a bottle products is that some of them have "patented" bacteria or bacteria with names they don't want to release, which seems kinda like it's not just the regular trustworthy nitrifying bacteria we've always used as aquarists. I'd feel more inclined to buy more bottles of patented bacteria cause I'd think that's what's in my filter, rather than a more natural form. Of course, I'm no expert on the subject.
All in all, countless reviews of people say these products don't work, plenty of people buy them and come to this forum with a tank that started off with them, but still isn't cycled yet. I don't find any point in trying to take a short-cut when it comes to developing the most fundamental part of an aquarium, when there's a proven, sturdy way to do it with 2 dollars of ammonia, a test kit (which should be kept at arms reach anyway) an eye dropper, and a little patience.