Check Dark Exchange, p2px, bitcoinx. Dark Exchange is open source but I think it's kind of abandoned (lack of interest).
Just looked into your suggestions, p2px is vaporware,
Dark Exchange holds promise as a simple p2p version of #bitcoin-otc or bitcoinary... -But not intended to do real time trading.
Dark Exchange is the truly P2P way and it cannot be any other way without introducing banking in the system, which then makes it less P2P.
Bitcoinx appears to be the whole enchilada, and it is an exchange for anything of value at all, but I don't know if it has real-time trading either. I'll talk to them about the specifics.
For these things to catch up I think you'd need traditional exchanges to completely stop working or be so unreliable people would need to hedge elsewhere.
Actually the way I've got it in mind, it can actually compete with the traditional exchanges, and additionally incentivize their own existence too, much like how bitcoin mining works.
I commend your efforts, but there is simply no way P2P will be competitive vs a centralised + liquid exchange. People will arbitrage the hell out of it until it makes no sense for 90%+ of the people to use anything else than MtGox or whatever centralised exchange is there.
For it to truly catch up massively, you need all popular exchanges to fail and fail very badly.
However it will still be useful as a minor alternative.