The generator is easy to use, and it offers the ability to create 3 5 or 9 pixel corners. I was using it with Firefox and I could not select the 3 or 9 pixel corner options. It appears that the other options are not available yet. The 5 pixel corner is nice and the html and css appear to work well. I did not test it extensively, only in Internet Explorer 7 and Firefox, so don’t quote me that it works in all browsers.
The license for Spiffy Corners states:
May be used for personal and business use, but may never be sold or used in a product that is not free without my consent.
You should be fine if you want to use the code in your own website. If you charged for access to your website you might have a problem, but I could be wrong about that.
Overall Spiffy Corners is a nice html/css generator for corners. It would be nice if the options for different sized corners worked, but perhaps that will come in the future. As for the project I was working on that needed rounded corners, I ended up using images in the end. Perhaps on my next project.