Also, Arroyo is in the National League, and in a much easier division than the AL East, the Cardinals and Stros have been sub-par, and the besides them and teh Breweres there aren't teams that can even come close to friggin' Tampa. And the auto-out in th 9th spot has also got to be helping Arroyo's ERA, which is coming back down to earth. So he wouldn't be the same pitcher if he were back here.
On anotehr note, the real tell-tell on if the trades a bust or not will come in the future, if Pena reaches his potential, and when Arroyo leaves his peak years, which he is in the middle of as we speak.