The $4.99 version includes a tool called Snapshots: Take a photo of a wine label, and the app will identify it and price it for you, allowing you to find out where to buy it, save it to a wish list, or identify it as a wine you have in your cellar. (The free, ad-supported version doesn't include the Snapshots feature.) It works pretty well; it almost always identified the wine label, if not the varietal.
The wine searching feature isn't perfect. Will it ever be possible to search for wine effectively? You can identify color, price range, country of origin, some flavor profiles, or varietals. A search for red, spicy, and earthy under $8 turned up an M. Chapoutier Crozes-Hermitages Petite Ruche 2007. Great, I can get it for $4.95! If I'm in Wien, Austria. So I re-sort the list by distance instead of price, and the wine is suddenly nowhere near under $8—more like $25. One reviewer says "really good value for what you pay," but is that referring to the $4.95 Chapoutier or the $25?
BTW, Snooth: There's a typo on your iPhone app. I don't really want to search for desert wines (would prefer water in that case, please).