Some of this covers earlier posts. I've converted to "No Groups", Mobileme based calendars in iCal.
> Export each calendar. (iCal>File>Export)
> Convert to new Mobileme calendar (mCal, I call it.)
> To preserve groups, import exported .ics files into either existing mCal calendars or new ones. For example, I had a group called "SigEp Davidson" made of "SigEp Chapter", "SigEp National", "SigEp Alumni" and "college". I created a new mCal calendar called "SigEp DavidsonX" and imported each component calendar into it.
> Visually compare "SigEp Davidson" with "SigEp DavidsonX". I did this by syncing, then opening "SigEp Davidson" in iCal and "SigEp DavidsonX" in Mobileme and comparing the two windows. Syncing up to Mobileme may be very slow depending on the number of events. I decided to sync and check after each import as that made it easier to check. Be patient and let the sync do it's job. I did not do it, but a faster way to check would be to print the "SigEp Davidson" and "SigEp DavidsonX" files and comparing them while they sync.
> When I began I had three groups and all calendars, grouped or not, totaled 29 including subscriptions. When I concluded I had 11. I like the 11 more than the 29. The reduction was combining groups and combining some individual calendars. I've found it easier to manage fewer calendars.
> Syncing works much faster from Mobileme to mCal rather than mCal to Mobleme. For this reason I entered calendar events that were new into Moblileme rather then mCal during the process when I had both windows open.
> Importing works only into iCal or mCal. I could not import into Mobileme. I imported into mCal, which went quickly, then synced with Mobileme, which went very slowly.
> I have an iPhone 3G which I cord synced to update.
> In the iPhone 3g go Settings>Mail, Contacts, Calendars>.Mac>Calendars and turn calendar syncing with mobileme On. Let iPhone update itself.
I've not used Time Capsule backups of iCal since I'm Mobileme. On another machine that is not mobileme I've used backup calendars found at Enter Time Capsule>Date>Home>Library>Calendars. The names of backup calendars are pure geek, not what you see in iCal.
My wife is Mobileme. She has no grouped calendars, using the calendars assigned by Apple. Converting her was letting Mobileme do the conversion then turning in syncing in her iPhone 3G. Her calendar continued to appear on my iPhone and MacBook Pro and my personal calendar after four imports continued to show on hers with the imports.
In each case we're running the most recent software.