You are right, having it alone will not make you lose the weight but there is something to be said for awareness.
I am finding it triggers some of my slight OCD tendancies so I do laps around my house at night to get in the steps to make my goal for the day. I also find I have to work more than I thought I would to get my step goal for the day if it is not a run day.
I've tried several pedometers over the years but I forget to put it on, it falls off, it gets lost, I break it etc. The flex is great because I wear it and forget it.
It is also slightly illuminating to see how little sleep I am getting. I know I don't get enough sleep but when I get to the end of a week and see that I slept less than 5 hours a night 5 of 7 nights I see why I'm tired. Its easy (for me at least) to brush that off. Getting only 4 hours of sleep a night is hard on my health and effects my fitness levels so being aware that it was not an isolated event for the week helps me to try to break the cycle.