v0.6 beta [Apr 28, 2012]
-more than 20 language localizations
-Initial network synchronization should be much faster (one or two hours on a typical machine instead of ten or more hours). -Backup Wallet menu option.
-Bitcoin-Qt can display and save QR codes for sending and receiving addresses.
-New context menu on addresses to copy/edit/delete them.
-New Sign Message dialog that allows you to prove that you own a bitcoin address by creating a digital signature.
-New wallets created with this version will use 33-byte 'compressed' public keys instead of 65-byte public keys, resulting in smaller transactions and less traffic on the bitcoin network.
-The shorter keys are already supported by the network but wallet.dat files containing short keys are not compatible with earlier versions of Bitcoin-Qt/bitcoind.
-New command-line argument -blocknotify= that will spawn a shell process to run when a new block is accepted.
-New command-line argument -splash=0 to disable Bitcoin-Qt's initial splash screen validateaddress JSON-RPC api command output includes two new fields for addresses in the wallet: pubkey : hexadecimal public key iscompressed : true if pubkey is a short 33-byte key New JSON-RPC api commands for dumping/importing private keys from the wallet (dumprivkey, importprivkey).
-New JSON-RPC api command for getting information about blocks (getblock, getblockhash).
-New JSON-RPC api command (getmininginfo) for getting extra information related to mining.
-The getinfo JSON-RPC command no longer includes mining-related information (generate/genproclimit/hashespersec).
-BIP30 implemented (security fix for an attack involving duplicate "coinbase transactions").
-The -nolisten, -noupnp and -nodnsseed command-line options were renamed to -listen, -upnp and -dnsseed, with a default value of 1. The old names are still supported for compatibility (so specifying -nolisten is automatically interpreted as -listen=0; every boolean argument can now be specified as either -foo or -nofoo).
-The -noirc command-line options was renamed to -irc, with a default value of 0. Run -irc=1 to get the old behavior.
-Three fill-up-available-memory denial-of-service attacks were fixed.
