Executive summary: if you are a p2pool or solo miner you should upgrade before the switchover date (April 1, if all goes well) or there is a good chance you'll produce nothing but orphan blocks. I welcome suggestions on how to effectively get that message out to the community.
Quick clarification on this, Solo miners need only upgrade the bitcoin client they are mining through in order to ensure generated blocks are "clean".
But, with P2Pool, because it's peer to peer. Would not EVERY P2Pool miner need to upgrade their clients or else the entire pool could be affected? (example being I'm mining against P2Pool, I'm using an updated client, but joebob is also mining on P2Pool with an old client. If his client happens to be the one that finds the block, even though I've contributed shares towards said block, and he includes the invalid tx, the whole block, and all contributing miners to that block get screwed correct?)
If this is the case, that's a pretty big problem for P2Pool miners. Because there is no way for us to know if the rest of the pool is updated. (and it essentially opens up P2Pool to a DOS attack vector. Anyone looking to take down P2Pool can join up with bogus clients and mine to start injecting bad blocks into the mining results for the whole pool... Sure it would only be proportional to the mining power brought to the table by the "attacker" relative to the rest of P2Pool, but it's still an attack vector).
Also what classifies as "upgraded". (ie: I'm running the latest official client from bitcoin.org, but not a dev branch. Do I need a dev branch? if so which version specifically)
Thanks!