I would absolutely do this deal. Biedrins has more potential than Perk, and Ellis is a star (although I am little worried about how he will fit with Rondo). Honestly, the only place Perk has an advantage over Biedrins is in covering Howard and Shaq...however, the C's still have Wallace, KG, and Davis, all of whom have shown they can give Howard nearly as much trouble as Perk does (I am really wondering how much Clifford Ray...who also coached Howard in his formative years...has to do with that).
A deal like that gives you a tremendous young core of Rondo, Ellis, and Biedrins, to go along with Pierce and Garnett.