I am very optimistic about my favorite team, the Atlanta Braves. The Braves were really one of the top 2 or 3 teams in the National League last year. Their record did not show this, but their stats did. That makes them an easy pick to improve.
I am also optimistic about Jeff Francoeur. Jeff's big weakness has always been his plate discipline. He nearly doubled his walk total and rate last year. This was reflected in his increase in pitches per plate appearance. His home run total was down last year compared to 2006, but his doubles(40) were way up. It's easy to feel optimistic about a young player who is showing more patience and hitting a lot of doubles. Not to mention that he is hitting behind a pair of guys who regularly post .400+ OBP (Chipper Jones and Mark Texeira.)
So if the Braves can just get enough pitching out of their rather old rotation (Hudson, Smoltz, Glavine, Hampton) then it should be a great year. Contrary to popular belief, Turner Field is a hitter's park. People think it is great for pitching just because the Braves had so many great pitchers for so long. It's not. It's actually at the second highest altitude of any MLB park, next to Coors Field of course. So the Braves are going to once again going to score a lot of runs.
Finally, gotta mention the local teams. I don't know what to make of the Oakland A's. I think they will surprise, but then again expectations are so low that they almost have to. The Giants on the other hand are going to be miserable, and they deserve it. They were just a little too happy to get rid of Barry Bonds, the guy who built their current stadium and gave them a future as a big market team (once they finish paying for the stadium.) I do hope to catch a Tim Lincecum game though...