my family setup
Perhaps it will help if I explain things in a different way.
My iphone 4: Every account is my Apple ID which is also my main gmail. icloud, imessage, apple store. Under icloud, i turn on what i want to share with ipad. Photo stream, reminders, bookmarks, find my iphone. I don't worry about contacts, calendars or email because i use gmail and google sync. If i wanted to use apple's email (a me.com address), i would create one and associate it with my apple id.
My ipad 2: Set up same way as my iphone 4. Every account is my apple ID. Share's app data, bookmarks, photo stream, reminders. Shares imessage with my phone.
My wife's iphone: Used my apple ID for apple store since we all use same account. Used her apple ID (her gmail address) for icloud and imessage. Most options turned off in iCloud besides find my iphone. Why? There's nothing to share it with such as an ipad. I wouldn't want to share with her because icloud share's data. My angry birds would be her angry birds..
ipod touch (daughter's): Used my ID for apple store since we all use same account. And created her an apple id (her gmail address) for imessage and icloud. Again, turned most icloud off. She doesn't have other devices to share with.
Backups: Use main computer for everyone. I don't use icloud for backing up anyone. It doesn't really handle video. I'd prefer full backups. But back to video, if i'm syncing to itunes to get videos off and on, why complicate things? Just sync it all. Maybe this will change later... Or get ironed out. At least there's wifi sync now.
Itunes Match. Don't see a need for yet.
Hope this helps anyone. Maybe i missed something or not seeing something. Feel free to comment.