It's not a very cohesive set: the perspectives are all over the place and there are like four different visual styles being used.

Some icons are shoddy and I don't like the harsh jewel aesthetic used for a lot of them.

I wouldn't recommend using these.

I agree. It's a shame. The gesture should be applauded, but the icons really are not very useable. The Silk icon set is much better.

Pretty, and a worthy addition to the list for side projects and quick prototyping for things where I don't have budget yet.

For projects for actual business (your employers' or your own), I suggest investing in getting design a little more specific to the actual customers' needs than most stock free icon sets. This one, for example, would be grossly inappropriate for my non-technical customers, who are not yet up with the reflections on top of reflections Web 2.0 aesthetic. (I got my icons for them from http://www.icons-icons.com two years ago on sale for $25 and its probably the best $25 I ever spent in my life.)

New rule of iconography: Never, ever use an icon of a guitar for anything that doesn't specifically have to do with the guitar. Guitar-fingering-tutorial app? OK, you can use the guitar icon. General music recording/composition/mixing/production app? NO GUITAR.

You should demand your money back.