Key scrambler: useless because the attacker can read the key from bitcoin-qt process's memory.
key scrambler is to prevent keyloggers, not the private key. If the attacker gets a hold of the private key of the encrypted wallet, does he still need the passphrase?
No, the private key is what they need. If your wallet is encrypted, your private key is encrypted until you enter a passphrase which then unencrypts the private key into memory for a set amount of time. The private key controls the coins, so obtaining the unencrypted private key is basically the end-game for any hacker. I'd rather see the built in bitcoin-qt encryption refined, so you can control encryption types, similar to truecrypt.
