Although this was a bizarre occurance that Mike Franseca broke a news story that the Mets have an agreement with Jason Bay, I will tackle it as it is official.
4 years, approximately 65 million, and a 5th year option that most likely will be vested to make it 5 years for 80 million. He gives the Mets the much needed power that they need and his defense isn't as bad as everyone thinks. He isn't a gold glover, but he is average, and heck, he is better than Gary Sheffield and Daniel Murphy who butchered/patrolled left field last year.
It is a lot of money for an "old 31" year old, but I dont think it will sink the Mets if he doesn't perform like an 80 million dollar player. There is very little upside that he'll outperform the contract, but I don't think there is much risk that he completely underperforms it.
What I'm more concerned with is what Omar's next move is, and I hope it is pitching, not Bengie Molina, but nothing will surprise me with this team...