To all pool operators, solo miners and p2pool miners; I have an announcement.
As everyone well remembers, we are upgrading the block-validity rule of Bitcoin to support short multisignature addresses. We realize that upgrading the code that you've been using for a long time is at least inconvenient and, for some of you, even painful or scary. But in the case of BIP30, which went into effect with the appropriately safe network support on March 15, it was necessary and in the case of this announcement the long-term benefits will far outweigh the short-term costs of this transition.
Therefore I'd like to announce that support for BIP16 has acquired a majority of mining support needed to prevent a potential permanent fork and will be activated on April 1st as previously planned.
This chart shows support over the last week: http://blockchain.info/P2SH. Support is well over 70%.
So if you are a pool operator, solo miner, or p2pool miner you need to upgrade your Bitcoin-Qt/bitcoind before April 1st. Running a version of bitcoind earlier than 0.6 release candidate 3 past this date means running the risk of potentially wasting your hashing power mining invalid blocks since earlier versions will accept invalid spends of BIP16 transactions into their memory pools and will put them into blocks considered invalid by the majority.
p2pool users will also need to upgrade to the latest version of p2pool.
If you are a miner connecting to a mining pool, you can ignore this message.
For non-miners: version 0.6 also contains several important bug and denial-of-service fixes, so if you can, upgrade.
Backports of the BIP16 code to earlier releases are available if you are running a patched bitcoind. Patched binaries of older releases will be available soon.