Question.
Unlike in the video, do you have to push the home button each and every time before you speak to Siri?
Not always, you can see he is pressing cancel after some commands

It does, however, depend on the command you gave it as to whether it waits for another command or not.
and yes, it does calendaring/appointments too.
When telling it to make a note it Prompts you if she should store your notes in her memory or in Evernote if you have it installed.
It'll be even better with the new voice engine in Android 4 that doesn't need to upload your audio to servers to be analysed as it's done on the phone, then the command to be sent back down to the phone so it'll be quicker and no waiting around for a second or two for that to be actioned.
Need to borrow someone's iPhone 4S and start a convo between them, see what happens
I can see the novelty wearing off soon, I used Vlingo and Google Voice Search before this, which are good and do what they say on the tin but don't interact with you like this. Modified my avatar too:
from

to hot librarian

Strange she didn't pull a face that time I asked, normally she frowns if you say something perverted

and does weather too

A bit squished but my phone is low resolution and only a 3.2" screen, but the ancient CPU copes well so can't see why Siri can't work on the 3GS or 4 tbh