I have to say, I really like the Yelp app on my iPhone. Of course, I'm in LA where there are plenty of full listings for all kinds of things; I can see how Yelp might not be quite as useful in a less populated area. But when I need to find a new restaurant or where a certain retail place is, I've found myself pulling out Yelp as a location app even more often than the iPhone's built-in Maps application. Not to mention that the Monocle feature is a fun demo when I happen to be out and about with friends.
Now Yelp has been updated to be universal, running on both the iPhone and the iPad. It's not quite as helpful on the iPad without a 3G connection, of course; I tend to use Yelp mostly when I'm out and about and need a quick address or map pin. But Yelp also has lots of user reviews and information about various businesses, so even when you're at home and thinking about going out, the app can be useful. And what the heck, it's free.
The update also includes some bug fixes for both versions, and it's a free download from the App Store right now.