I wasn't happy with the Arenas deal either--being the basket case that he is. But with Lewis continuing to struggle in his game and the lack of confidence his suspension last year had brought him, I think it's sufficing to say that the trade was somewhat in the offing for him (didn't expect to get Arenas in return, though).
On the other hand, getting rid of Carter is a big plus for the Magic. He was and will never be the go-to-guy the Magic had expected from him. Carter thrives on being the sole ball-hog of any team (Nets-Raptors), and also, being an injury-prone clearly puts him less than a shadow of what he was before. I think Jason Richardson can be a good fit on the Orlando offense, and not because of the Suns' system, but of Howard's tendency to attract the defense down-low. The only problem I see now is the crowd it apparently created for the PG/SG spot with Nelson, Arenas, Redick, Duhon, Williams and J-Rich alternating.
Sad to see Pietrus go, though. I think he's the Magic's second best defender next to Dwight.