I use it as a personal tutor. It is really good at it, because it can respond to clarifying follow up questions and it is usually right. For pure development or peer review, it is not there yet. I asked it recently to help me decipher some real life SQL performance issues and it did not really help. Actually, it turned out to be a waste of time. The classic Postgres query analyzer and some 3rd party query visualization tools got the job done.