How do you prioritize what feature you should build?

Here's how I like to look at it (in order of weighting):

1. Does this feature get my customer closer to fully solving the pain point I set out to fix with this product? Does it save them time or money?
2. Have any of my current customers requested it (or something similar)?
3. Do I see customers of competitors asking for this?
4. Do I have the staff and time resources to implement it?
5. Can I add it without detracting from the existing experience (ie, is it just clutter)?
6. Is it an innovation that gives me a competitive advantage (this plays into timing)?