However, not that fast.
My iPhone (come on, isn't is the greatest thing since sliced bread? :) can sync with iCal (not a decent approach for cloud-computing trending era), but fails to show any other calendars attached to my account. In addition to such a boomer, it gets synced with the weirdest name you can imagine (but who cares). I've also tried setting up a separate CalDAV account for calendar on iPhone as well as establishing Google sync through Exchange protocol - none of these things can show any additional calendars (called delegates in iCal).
Here is an idea. While so trendy cloud-computing managing panels are growing so fast, it looks like people managed to miss very basic things. The managing panel for Mail-AddressBook-Calendar kind of stuff. That has inputs and outputs, and dashboard. Manageable with drag and drop. Say, I want the Google Calendar, Google Mail and Yahoo Address Book (or, screw it, just native Mac Address Book.app). These are inputs. Outputs are connectors to any type of software you can imagine. Dashboard is one screen that allows to work flawlessly with you stuff. That's it. That easy.