The goal of this is not to look at what Oakland did, but what they didn't do. Obviously most Oakland fans were very pleased at the activity of their GM, and are glad that his name doesn't end in Sabean. However, there seems to have been some opportunities missed and with my 20/20 hindsight I can pretend to be smarter then Beane, emphasis on "pretend".
Starting Rotation - How can you hope to contend against the Angels with such a terrible rotation? Not that it won't be there in another year or two, but going in with Duchscherer, Eveland, Gallagher, Braden, Pitcher X (Probably Gio); you have to realize how fragile that group is. I am not sure if Beane had wanted Sheets before he realized that he was damaged goods, but it appeared that starting pitching was not a concern. A small effort was made to acquire Randy Johnson, but at the price he signed for combined with the fact that he signed with a terrible offense suggested that Randy REALLY wanted to stay in the NL West or that the A's didn't try hard enough. While I don't believe the answer was in free-agency, I felt a trade for a reliable starter on a bad team (i.e. Gil Meche) was in the cards. Oakland has a great young staff, but it does need some guidance. Sometimes trading a prospect is the right answer.
Relief Pitching - I hate paying good $$$ for relief, although I understand its importance. Ziegler, Devine, and Casilla are all great options and adding Russ Springer was a solid move. The A's had the money to spend and I feel pretty good with our options once our starters get the pat and hand the ball over.
Outfield - Left field was given the biggest boost it could. Sweeney in center is great too. The problem is in right field. Bobby Abreu & Adam Dunn - Obviously both do not fit into the same Oakland roster together, but both came at amazing bargains and letting Abreu sign with the Angels might be enough in a close race to give them the edge they need to win the West. With the Giambi signing both would be slotted into RF (or maybe to DH with Cust), but your overall line-up would become:
Abreu or Dunn would provide anywhere from 10-25 more HR's and a much higher OBP than a full season of Buck, while providing worse overall defense (although sometimes Buck can be pretty bad).
Infield - No complaints. The organization did everything it could to sign Furcal. Meanwhile, although we did not know it we were being used as "the other woman". OCab is more than acceptable, while Nomar is a great back-up choice for his bat, glove, and experience. Ellis came cheap and is great in the clubhouse and Giambi is just what this club needed. If Chavez/Nomar prove to not be healthy and we are in need of a 3rd basemen to be competitive, Scott Rolen (if healthy) would not be a bad option in July.
Overall, the lack of a good, reliable starting pitcher and letting Dunn/Abreu slip by was really hard. With Duke already having problems a young rotation will need to really step up. Hoping the community can point out where I am wrong/right and help me understand the moves NOT made more.