On the plus side, the app has all the conversion options I could think of needing and is pretty easy to use.
On the down side, the program only lets you remember 3 favorite conversions, and doesnt remember the units last used for any other conversion. Thats fine if you regularly need to convert Argentinian Pesos into Australian Dollars or miles into nautical miles, but otherwise it can be cumbersome.
It would also be nice if the number auto cleared when you switched conversion units - it currently just appends to the existing number.
But for $0.99, its a reasonable value.
asterix135 about Units - Unit Converter for your iPhone