I LOVE Lose it. I track what I consume and what I burn and I use it.

But I've always done that.
I tend to underestimate just to be on the safeish side and it hasn't done me wrong yet.
I'm SO glad in the new version that you can adjust your calorie goal for the day. They one they set for me was too low and I had to up my weight 20lbs to adjust for it which was annoying.