I’ve downloaded a lot of free applications for my iPhone from the App Store, in fact I have 4 screens almost filled. Unfortunately many of them are worth exactly what they cost.
My worst experience so far has been Go Figure Lite, a simple calculator with built-in unit conversions. Instead of a keypad, it uses sliders to enter values, which are nearly impossible to set accurately (one of the reviews in the app store points out that double-tapping will bring up a keypad). Aside from that, the first conversion I tried was wrong. I entered the current temperature, 68F, which it correctly converted to 20C. However, when I went the other way, it converted 20C to 99F.
I also found that many of the location-based applications such as Yelp & Where don’t work here in Vancouver, since they seem to have US locations only in their database.