a) Siri won't work at all, or will degrade to something like Voice Control, if the server is unreachable or you're out of coverage;
b) all of your dynamic data (address book, calendar, etc.) needs to be synced to iCloud for Siri to see it;
c) third-party extensibility won't be available until iOS 6+.
a) Siri won't work at all, or will degrade to something like Voice Control, if the server is unreachable or you're out of coverage; b) all of your dynamic data (address book, calendar, etc.) needs to be synced to iCloud for Siri to see it; c) third-party extensibility won't be available until iOS 6+.