This is what the boyfriend and I have been doing, and we've been at it for 2 months now. I'm down 13 pounds, he's down 19, and I wouldn't say we've been super diligent (there have been friday night fish fry dinners, happy hour afternoons, etc.)
What I love about MFP is that it keeps you aware, more than anything. If I have a glass of wine, I know what I've just put into my body, and that makes it less likely I'll have an entire pint of Ben and Jerrys ice cream. Even if the app over-calculates, I try to at least log the work I'm doing.
Also, as a vegetarian, I've been focusing on sodium and protein - pre-packaged foods often have way more sodium than necessary, and protein is hard to come by in veggies. So it's forced me to be more creative about my nutrition. I've learned to like kale, eggs, and beans a lot more than I thought I would.
