My biggest disappointment in Siri was learning that most of it runs "in the cloud." My biggest use-case for it was going to be dictation. I honestly thought that they had managed to get a voice dictation engine running on the A5 directly.
I take road-trips frequently, and frequently I hit areas with very spotty coverage for long stretches...areas where both data and voice don't really work so well. But I can get an occasional text message through. Problem is, of course, that I can't read and respond to texts while I'm driving. That requires pulling over. So I want to be able to dictate text messages and have the incoming texts read back to me over the car stereo.
Of course, those same stretches where the only thing that really works is text messaging will prevent Siri from working, since she needs a reliable data connection to Apple's server farm to actually work. So, useless in this scenario.
So my biggest hope is that Apple will actively work to try to move more and more of Siri's functionality to the local handset, and out of the cloud. Especially dictation.
-- Nathan