MobileMe users can be invited to view and edit a calendar.
There is no support for subscribing to a non-MobileMe calendar. There is a mechanism for importing from Outlook or (bizarrely) iCal. It's not documented, but I believe Outlook import requires installing some Apple software (iTunes?) and I am pretty sure it won't work with an Exchange based calendar.
It seems users can't share on both MobileMe and publicly! If you make a calendar public you lose the miniscule sharing icon to the right of the calendar name. Weird.
There's some iCal integration, but, judging from a flurry of tech notes, there are lots of bugs. I suspect Apple wants pre-10.7 users to use the web UI and forget iCal. I assume MobileMe Calendar has good iOS calendar integration, but there's no iOS support for editing calendar-associated tasks.
Overall, I'd give Apple a C+ for this effort. If they were to add subscription they'd graduate to B-. The significant advantage over Google Calendars is simplicity and, of course, a far more pleasant UI. The disadvantages are substantial -- no subscription, no web publication, no embedding, etc etc.
Update 10/16: See comments for additional drawbacks. There have also been recent posts from vendors that used to be able to synchronize transactions with MobileMe calendars -- Apple has removed functionality they relied on ...
- Daylite: ... In the process of moving to the new calendar, Apple migrates your existing calendar and deletes the old calendar. In the process of deleting the old calendar, sync services propagates the delete to all sync services clients. Daylite obeys these delete commands (as it should) and moves your calendar data to the trash (lucky we have a trash).
We've communicated with Apple during the MobileMe Calendar beta and we are looking into possible solutions.
- Spanning Sync and the New MobileMe Calendars (Spanning Sync Blog): ... Spanning Sync can sync the new MobileMe calendars to Google, but changes made in Google won't show up on your MobileMe calendars. Unfortunately, Apple specifically disallows syncing of the new calendar format (called CalDAV) using its Sync Services architecture, which Spanning Sync is based on. Spanning Sync can read from MobileMe calendars so "one-way sync" is possible, but making changes to them is currently impossible... we're hopeful that Google will enhance Google Calendar so that it can sync directly with MobileMe without any intervening software. Google is tracking the request for this feature here ...
I imagine Daylite couldn't warn customers due to their beta agreement, but since Apple ignored their concerns their customers have been screwed. Spanning Sync suggests customers revert to the old format.
Apple is not a "nice" partner or vendor, but we already knew that. They are not the best of all worlds, only the best of our world.
I grumpily added my bit to the Google feature request list, though, in truth, I don't use MobileMe because I know Apple won't deliver what I need. I'm not their customer.
The only upside to this story is that MobileMe is using CalDAV, so there's a potential for a better future. I bet OS X desktop support will require 10.7 though, and that OS won't be safe for my use until early 2012.
There's been rumor of a rapprochement between Google and Apple. I hope that's true, because for geeks like me the best solution is combine the best bits of Google with the best bits of Apple (not including MobileMe).