The best product builders are both ruthlessly self-critical AND filled with positive faith in the product. They have enough faith and belief to fully commit themselves to the creative endeavor. At the same time, they have the strength of character to see clearly how their product is really quite lousy and can be so much better. You have to have a strong character to keep the pressure on. As F. Scott Fitzgerald said, “The test of a first-rate intelligence is the ability to hold two opposed ideas in the mind at the same time, and still retain the ability to function.” Great product people must believe — and be very critical — at the same time.
Ooga Labs 
Hello James,
Right on! A key to improvement is the willingness to look honestly within. A positive attitude greatly helps to persevere in making difficult changes. These truths hold for human personality as well as software products. As a product manager, I always found my best tool was a pair of large ears, willing to hear what customers were saying without being defensive.
As companies/products mature, formalizing a feedback loop with Customer Advisory Boards can help. This article describes one enlightened example.
Best of luck.
Marc
Oops, I left out the juiciest part, the article’s link:
http://www.startuplessonslearned.com/2009/10/real-customer-advisory-board.html