Yes on multiple calendars.

I've only skimmed over the code at this point and haven't actually tried it out yet, so I can't answer on the shared calendars yet (though I'm guessing yes).

No on contacts.

I personally want to see all of these supported (in addition to tasks) and plan to help making them all happen. I've been sorta waiting to jump in until after the next release so I can see how lorelei is wrapping the calendar-backend API for use from python. There are other little improvements I have in mind from skimming the code last weekend, like preserving colors from google calendars and preserving the read-only flag on calendars (not sure what happens at the moment if you add an event on your n900 to a calendar that is a read-only google calendar).