Alyssa Dver tells us what distinguishes a great product manager from a good one. Great product managers:
1. Know their product but also know their own limits.
2. Listen first.
3. Ask why, not what.
4. Are decisive.
5. Are responsive.
6. Communicate frequently, concretely, and concisely.
7. Manage passion.
For details, read the rest of Dver's piece.