After much fruitful discussion and evolution, this proposal is now a series of "Bitcoin Improvement Proposals" -- see BIP 11, 12 and 13: https://en.bitcoin.it/wiki/Bitcoin_Improvement_Proposals
Sincere thanks to everybody who contributed improvements, ideas and code.
Oh, I just saw your comment just now after submitting my own. Great!
Btw, @gavinandresen, I forgot to say thanks for all your hard work :)
EDIT: for some reason the reply I sent by my phone (prior to your last comment) didn't post to github. Here it is:
Like most things, this could have been avoided with better communication. The following would have done nicely:
"Support for this minimum feature set is needed for 0.5's improved security features. The security of the whole network is improved by adding these transactions immediately. Support for generalized m-of-n transactions will be added as soon as a consensus is reached, but we deemed it necessary to split the process into two stages so as to get these new security features out the door ASAP."
FYI, for the future.
I can update my pull to implement the latest version of the generalized proposal within two weeks. I have not been motivated to do so because of the issues that @maaku raises. If such a pull will be seriously considered I can go ahead.
I don't see the problem with wallet security/backup on top of the generalized case. To get the a AND b OR c case, just use 2-of-2 OR 1-of-1.
Two weeks will be too late for the 0.5 release, and you'll need to split your PULL into two parts (just the IsStandard() changes and then another pull that adds RPC commands to generate the transactions; the IsStandard part has to be released first so users don't start generating might-take-days-to-confirm transactions).
I'm surprised you feel like all of this isn't being "seriously considered" given the amount of discussion and back-and-forth.
@gavinandresen - I feel that there is a reluctance to accept substantial contributions from the community. As @maaku I am also concerned about community trust and I think the success of bitcoin project depends on that and good communication. A decision was made even though the balance of arguments seemed in favor of the generalized solution.
As to code complexity, the IsStandard part of pull #319 is very simple - https://github.com/bitcoin/bitcoin/pull/319/files - wallet.cpp line 1125 to 1179. The only other part is a refactoring of Solver in script.cpp that is generally useful. Extending this to multiple OR clauses will be only a few more lines of code.
Please consider including the 2-of-3 case. This would enable simple escrow - buyer, seller, arbiter.