I lost about 30 pounds using Myfitnesspal thanks to recognizing just how many calories I was putting in my body. The app alone wasn't enough, I had desire and this was a tool (I'll say it until I can't speak any longer, technology is just a tool, you have to use it right).
Beyond the app and my desire, was a friend and colleague David Kennealey who still to this day beats me up over the sugar content I put in my body (and beer content as well). David is a key reason I still log in every day (340 days today!) because I know he is watching me. I don't completely log everything like I used to do, but that daily check in reminds me to watch my calories. Some days I put in everything, other days it's breakfast and I get lazy after that. But I still think about what I'm putting in my body.
I also use MapMyFitness which I have very few "friends" that use it. I use it not because of the accountability to friends, but it is a great app for tracking my runs and it synchronizes with myfitnesspal making it easier to keep up my diet. It's not the best running app, but it is pretty good.
I had fitbit and loved the community but keeping 3 apps current was a pain. I also hate wearing anything on my wrist. I tried a samsung watch and I liked that, but the apps were not compatible with myfitnesspal.
Once I hit a full year of logging in every day to MFP, I'll probably stop. I almost made it last year but was out of the country and could not log in. I thought I did but it did not synch so I had to start over. If I gain weight, I'll be back on but otherwise my MFP days will be less rigid but I'll remain more active than most.
Perhaps I'll find the perfect app and get rid of MFP and Mapmyrun. I'll miss the community though. I'm sure David will find a way to bust my chops no matter what.