I don't question it's general usefulness for most people, given that most people are either relatively inactive but healthy or overweight/obese and struggling to impose any discipline. I deeply resent the assumption that my attitude to BMI is caused by self deception and weakness. It feels like an ad hominem attack to try to win an argument (very thoughtless in this thread, of all places) and very unjustified. Having been obese and dealt with it, I was a rock stable 10 stone 10 for a couple of years, which only changed because I decided to pursue different goals (including both strength training and getting more serious about cycling). I made those changes partly because I thought I'd become a little too focused on bodyweight goals; not panicking or obsessing when my weight changed a bit was an achievement. Adapting to strength training without either losing good dietary discipline or panicking and obsessing was also an achievement; the fact that personal and work disruption messed that up was a huge annoyance but dealing with it calmly, and when I had the time, was important. I don't post about my weight in this thread because I have no doubts about my ability to reach my goal, having now achived much tougher ones on a regular basis.
It's precisely because I am able to be disciplined and honest with myself about my weight and health that I don't find BMI very useful. There's really no danger of my ever being obese again and I don't expect to see myself approaching a BMI of 25 again (I hope never to have the same nasty combination of personal and work circumstances and I'd be more prepared for it next time). If I'm wrong about that last part, I know that I'll be concerned about it quite some way before BMI proclaims me overweight. Conversely, I also remain convinced that 10 stone 5 is not a healthy goal for me. At 10 stone 11, I never met anybody who thought I was anything other than slim, I felt healthy and looked good on it. When I pushed lower, even people who'd only known ever the slim me became concerned for my health (OK, so my mum thought I was anorexic when I reached 11 stone but that's mothers for you). I do not feel deluded in this, or in my decision to aim for a slightly heavier goal with a significantly different body composition.
In short, I expect to spend the foreseeable future thinking (if I think about the BMI at all) 'Still in the "ideal" range, still not at the "optimum" 22.0. Now, how do I really feel?'
And that's my last word on this. I feel insufferably smug just having typed the previous paragraph and never looked to be typing any such thing in this thread.
