Hello :) author of the proposal here, if you have any question or comment feel free to ask!
Users that trust https://GreenAddress.it can check the instant confirmation inside their wallet (on a UI 'badge' similar to the N confirmations or unconfirmed).
While some platforms are interested in the instant confirmation some will take longer or won't.
For this reason and for external wallet users you can still manually check if a specific transaction is instant via https://greenaddress.it/instant provided that you are the recipient of the transaction and can prove it - and of course that you trust GreenAddress to not allow users to double spend.
The external instant confirmation link does not work for multisig or P2SH external addresses yet.
Link to the reddit discussion http://www.reddit.com/r/Bitcoin/comments/284me8/instant_conf...
Cheers!
Lawrence
