Ok, I've had this app on my phone for months and I've never used it..
I love using my phone, and I love checking in - my foursquare badge collection is testament to this, I just don't feel the urge to take detailed account of the food I eat, it seems to take away the magic of sharing a meal with someone. Lunching is my favourite past time after all.
Maybe it's a generation thing, I know people complain I'm always attached to my phone, but really I try and check in at the start of the meal and then leave it alone to enjoy the experience or eating out. I'd like to think I'd have no issue getting a 5% discount here.