I think it depends on the quality of your starting pitchers. Halladay, in my opinion is a top 3 starting pitcher. Year in and year out, he is as solid as any other SP, although he has had a rough spring training. Having Rollins will be a huge upgrade. All in all, I would say yes, pull the trigger. Rollins is a former MVP who will get a ton of stolen bases while hit for average. There isn't many great shortstops in the game nowadays and Rollins is top 3 after Ramirez and Reyes.