The main advantages of the tool compared to the competition are:
You can correct any lens you own, including e.g. third party wide angle converters.
You can easily make high-quality measurements yourself, i.e. the result is not based on manual tweaking.
The canvas size is increased for full quality of your pictures, i.e. no down-scaling of the picture. Canvas resizing is very rare for Photoshop plugins. (Because of this the plugin has to be started from the File→Automate menu.)
You can measure and correct all parameters – e.g. correct a non-centered and distorted fish eye.
You get both 8 and 16 bit color depth support.
Download from RapidShare