THere are no items you will need to take from one act to another. All the quests are act specific <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
Yes, but on the other hand set items lose their value after each act. Then they are no longer set items anymore.
The only items I took into *every* act were the books written in Ranaar language - I really wanted to get to know their contents ! <img src="/ubbthreads/images/graemlins/delight.gif" alt="" />