Hands-down, Yelp's biggest asset is its impressively large database of information. Not only is it able to pull up listings for even the most obscure-seeming restaurants and bars, but each each individual listing is also impressive in the number of details they contain. A recently added feature even lets you explore the menus of select restaurants, right from within the app. From a listing page, you can also place a call to a business, find directions, draft a review (but not publish it), check in, bookmark, add a photo, or add a quick tip.
My biggest issue with the Yelp app is its performance. When you're out and about, looking for a place to eat, it helps to have a zippy app that can quickly pull up listings, load reviews and photos, and find directions. Unfortunately, Yelp for Android is anything but zippy. While the newest version is certainly an improvement over previous ones, I still notice a lag, specifically when loading photos and pulling up maps.
Overall, the Yelp app is incredibly useful and well-designed. Some improvements I would like to see in the future include the ability to publish reviews, more filter options for search results, and overall faster performance. Even without these features, though, I would still confidently say that Yelp is a must-have app for every mobile user.