Giants are blessed with five really good starting pitchers- Cain, Bumgarner, Vogelsong, Zito, and Lincecum- all of whom are capable of big games but also some poor ones. Lincecum is the biggest question mark- dreadful first half of the season, greatly improved second half, some really fine middle relief in the post season, one pretty bad start- so he might be best used in key situations in a relief role. He seems to excel throwing 2-3 innings in middle relief, and they already have four starters.
I think Giants are in the catbird seat. Expect them to lose three of the first four, then win the last three for the championship.