In what appears to be a happy marriage, Where To? for the iPhone [iTunes link] now talks to the Navigon GPS app. You can select a category or search for a business and then transfer that information directly to the Navigon app for turn-by-turn directions. If you don't have Navigon, you get Google Maps directions instead.
This is a nice update because the Navigon POI (points of interest) database is contained on the app, while Where To? relies on Google information. This way you get the best of both worlds, with up to date POI info that can easily be picked up the the Navigon app for a pretty seamless experience.
While checking the app on a drive around town I found it quick and easy to find some specific places to shop. Restaurants are broken down into categories, including things like cuisine categories or other criteria like "all you can eat."
The Navigon link worked perfectly, and in real world use turned out to be handy.
The new version also adds contacts integration, and customization and deletion of categories. I liked Where To? when i first reviewed it earlier this year, and the Navigon integration is a welcome addition. Where To? is U.S. $2.99. If you don't want to spend the money, I'd suggest a look at Around Me [iTunes link] which uses the same Google data but doesn't link to any nav apps.