Related to a discussion I had in SF last week with some colleagues, here's his list of some of the qualities that make a great PM:
Strong interest in what computing can do -- a great interest in technology and how to apply that to problems people have in life and work
Great communication skills -- you do a lot of writing, presenting, and convincing
Strong views on what is right, but very open to new ideas -- the best PMs are not necessarily those with the best ideas, but those that insure the best ideas get done
Selfless -- PM is about making sure the best work gets done by the team, not that your ideas get done.
Empathy -- As a PM you are the voice of the customer so you have to really understand their point of view and context
Entrepreneur -- as a PM you need to get out there and convince others of your ideas, so being able to is a good skill
A long read, but worth it.