I’ve derailed plenty and it’s overall been drastically, wildly worth it. That’s because there’s no ambiguity that I’d be way overweight if not for Beeminder.
To clarify, I haven’t lost a lot of weight with Beeminder, just prevented my weight from going up without bound, as it has made very clear that it would otherwise do.
I’m very sympathetic to arguments that I could make food and exercise and lifestyle choices that would cause my weight to stay perfectly stable without thinking about it. If the things I do to stay on my Beeminder weight road were onerous enough, I’d prefer to make those choices. But the Beeminder weight graph is highly valuable regardless. I can make better life choices or better arrange my environment and make it easy-peasy to stay on my Beeminder weight road or I can skate the edge and do all the wacky things I do. But either way, not staying on it would be very bad and so it’s very valuable to have that graph. At worst your weight graph is a sanity check that just keeps you honest and ensures that all the other things you’re beeminding are in fact effective at maintaining a healthy weight. At best it’s what makes the difference weight-wise and literally saves your life.
Related question in another thread: Is it possible to maintain a healthy weight in a very unhealthy way?