Do you understand your audience? If you're building an application >for graphic artists, are you familiar with how graphic artists work? Are >you throwing out features that would be met with horrified stares?

Adding to this; You should understand who your audience actually is.

I believe Java went to a lot of sound engineers for designing their audio API... When it would be most likely used by people with no sound experience. I believe this is why Java's sound libraries are so awfully complex and hard to use. So this is definitely worth thinking about.