Woody can bring a lot to a team besides game wins. While those are important, if your team has a young pitching staff (and I'm not terribly familiar with SD, so I don't know what your rotation is looking like), Williams can be very valuable in a mentor role. His record this past season is misleading as well, as he lost a lot of 1 or 2 run games, which a pitcher for the Cards should not be losing. If SD's pitching coach is smart, and you guys can give him 3-4 runs a game, you got a good deal. I certainly wish him the best.
There's still a long way to go. I'm surpriseed nobody is consideering Randy Johnson. Schilling could stall out and be surpassed by his taller, uglier teammate. Johnson's got 15 wins and a better ERA than Schilling's (although not by much- 0.07).