I've been in United's Mileage Plus Dining program since October and haven't had any problems with miles being credited. As Anna said, they are a bit slow.

From talking to them on the phone it seems they send the mileage info to UA once a month. Given UA's "timeliness" in updating the miles on the website, that can make for some long delays in seeing some items on your statement.

My main difficulty is that there aren't enough places where I like to eat in the program. In fact, a few I do like have dropped out since I started. Still, as long as it's free and there are some places I like, why not

-QL