7+ IP, 0 ER (2012)
Chad Billingsley, Dodgers (8.1 IP)
Justin Verlander, Tigers (8)
Jered Weaver, Angels (8)
Roy Halladay, Phillies (8)
Jake Arrieta, Orioles (7)
Johnny Cueto, Reds (7)
The biggest surprise is clearly Jake Arrieta, who did not look like an ideal opening day starter for the Orioles. It should be noted that he was pitching against the Twins, who lost 99 games last year (although they do have Mauer and Morneau back in the lineup). If Billingsley (who has been a solid starter for 5 years) is primed for a great year, then the Dodgers are in great shape at the top of their rotation.
The Reds need Johnny Cueto to have a good season is they are going to make a playoff run. The NL Central is kind of up in the air with the Brewers losing Prince Fielder, but it looks very possible that the Cardinals will be tough to beat.
Weaver, Halladay and Verlander are all (as always) top contenders for the Cy Young, and their performances are not a surprise. There were elite pitchers that struggled (Lincecum, Sabbathia), so the Tigers, Angels and Phillies should feel very good. Although it is unlikely that the Orioles will make any noise in the AL East, Jake Arrieta might be a pitcher to watch out for this season.