How do you think the code should deal with the issue of "a fixed txid might no longer be valid" ? Or transactions that you THOUGHT had N confirmations and were in a block with timestamp T are re-organized to have M confirmations and are in a block with timestamp T2 ?
tcatm and I chatted in IRC about this problem-- he has the problem of how to keep the Javascript GUI (which shows you ever transaction) up-to-date.
Seems like you really want an efficient way of asking "Do I know about exactly the same set of transactions as bitcoind" (either for the entire wallet or for an account). That's assuming transaction data can't change (somebody double-check that assumption for me-- if the transaction data changes, then the txid changes... I think).
That led to some brainstorming of computing a hash of all transaction ids (maybe just XOR them all together). Or maybe something more complicated like a merkle tree... but that seems like overkill.
Is there a good, simple solution to synchronizing "I have this set of stuff, give me everything I don't have" ?