One of the big improvements is that multi-signature transactions, where both Alice and Bob have to sign to spend some money, used to require adding N signatures (number of signers) to the block chain to have a valid transaction. So it improves efficiency and should allow squeezing more transactions, but it also improves privacy, because there's no way to tell if how many parties are involved in the transaction.

Merkelised Abstract Syntax Tree (MAST) are the other big feature that allows for more complex scripting to also be represented in a compressed and obfuscated way (example in the link).