Efficiency in syncing the blockchain appears to be the number one priority of the bitcoin client developers right now. The next release, 0.8.0, will have major improvements in this area.
from https://bitcoinfoundation.org/blog/?p=16
"new features are being added to the protocol to support alternative implementations– next major release of bitcoind/Bitcoin-Qt (version 0.8) should support for “bloom filters” to get just the transactions relevant to your wallet"
"...optimize transaction storage so validating transactions requires much less disk access and memory..."
from https://bitcoinfoundation.org/blog/?p=16 "new features are being added to the protocol to support alternative implementations– next major release of bitcoind/Bitcoin-Qt (version 0.8) should support for “bloom filters” to get just the transactions relevant to your wallet"
"...optimize transaction storage so validating transactions requires much less disk access and memory..."