Ta'amu had intriguing size/strength - I have visions of him as a NT in the mold of Williams out in SD in his prime or any of those other huge NTs. Again, that was based on potential and college film, not as much on his production. Given his potential, I would have liked to see him get one more year in Pittsburgh. I understand the cut -- this is mostly the optimist in me.
From what I saw of Arnfelt, I think he could be an effective backup at DE. I'm glad that the Steelers kept him on the PS.