I've been a *huge* google fan for years now.  I'm tremendously excited about their current push which would leave everyone living in the cloud, and truly make the desktop irrelevant.  This includes their FTTH trial announced 2010-02-10 which would deliver 1Gbps broadband at a 'competitive price.'  http://www.google.com/appserve/fiberrfi/

To get back on topic, one thing (among many) that Google has gotten right is their calendaring.  There are a couple things to be aware of when working with google calendars, but since google enabled CalDAV access to a google hosted calendar, you can now manipulate that resource from standardized applications!

Limitation 1) There is no syncing of resources.  This is not to say you can't access or manipulate the calendar resource from an application of your choice, but it is to say you cannot sync multiple google calendar resources.  You could manually export/import, but you cannot automatically sync.  But Google has enabled some fairly comprehensive permission controls, so you should be able to accomplish everything you want from one calendar resource.

Limitation 2) beware of android!  Android can do a great job syncing all gCal resources you have rights to, but only through the primary google account bound to an android device.  This typically means a gmail account (I'm not sure if android will allow an apps account to be the primary).  So, even though I have an apps account with my office where my calendar is stored, I have to grant my gmail account access to manipulate that resource, which enables me to access the calendar from my android device!  Therefore, I simply add my gmail account with manipulation rights to any gCal I want to access, and all those gCals automatically show up in my android device.
With Froyo, android allows calendar sync from any google account (gmail or apps) associated with your phone!

CalDAV: http://www.google.com/support/calendar/bin/answer.py?hl=en&answer=99358#sunbird
iPhone: http://www.google.com/support/mobile/bin/answer.py?answer=138740&topic=14252
enabling mobile sync (exchange): http://www.google.com/support/a/bin/answer.py?answer=135937