It isn't a big deal for my situation to have all my calendars everywhere, more just annoying to see a calendar on my i devices that I have no use for there (a calendar I set up to remind me to do some maintenance items on my iMac). But I use Appigo's ToDo app on my iPhone, and it doesn't sync with iCloud yet so I'll just continue to sync calendars via iTunes and tasks with the Appigo sync utility.
I have found some other goofiness if I set Contacts up in iCloud, so even if I didn't mind having all contacts on my iPhone and iPad, I'm not going to sync contacts in iCloud until/unless those things are fixed. One is just annoying - contacts in iCloud doesn't properly sort all the contact names. Some are sorted by last name, as I want, but some random ones are sorted by first name. The deal-breaker for me is that, when I set up my iMac to sync contacts with iCloud, I could no longer edit distribution lists on the iMac to pick which email address to use for a particular contact.
Seems like iCloud is a little "beta". Hopefully it will get better.
Faye