I think this site is definitely appropriate for college level students taking music theory classes. I believe that some of it could be used by upper level high school students serious about a career in music. It is easy to maneuver through the site. I think this is a very educational oriented website and would work well alongside a music theory class. It allows you to look at musical works and analyze them. It also has a question and answer part as well. It has interactive exercises that allow you to work with intervals and chords. The music theory reference is wonderful allowing you to learn about scales, chords, intervals, and harmony.
I really like that the site can be viewed in English or Spanish. You do need Quicktime to listen to the music examples. On my computer it opens up another window to play the Quicktime music and you are not able to see the actual music then. There are no other problems with the site.