There's no word yet on the details of the one-year deal, but it should be safe to assume Byrdak will earn a reasonable amount of money for his role on the team. After the Mets wisely let Pedro Feliciano walk last year, there was some concern about filling the void in the bullpen, but Byrdak has been nothing short of excellent against left-handed hitters.
With his pair of strikeouts against lefties today, he's struck out nearly 33% of the lefties he's faced on the season. That's roughly twelve strikeouts per nine innings of work against lefties.
Byrdak will turn thirty-eight on Halloween, but as long as his salary is reasonable, bringing him back makes plenty of sense. Effective left-handed relievers may not be the rarest of commodities in baseball, but keeping Byrdak around is a good move.
Adam Rubin has some good quotations from Alderson and Byrdak here.