nice. i did read the thread, and the person wanted to sign into iCloud with a non-.mac or @me.com account. i just switched my AppleID from a yahoo address to a gmail address, and still don't even have a .mac or @me.com account, and my iCloud is active. it took all the contacts from my MacBook and iPad, all songs and apps from iPad and iPod, and everything is on my iPhone, and the iCloud account is syncing - without an "external" email address associated with any of it.
my understanding is that if you add other email addresses - i.e., gmail or whatever, and they are in your phone, all of those are backed up in iCloud, but i truly don't know. if you want to keep/move your gmail contacts or other email contacts into your iPhone, don't add it as Gmail in the iPhone, add it as Exchange, then leave Domain blank, and then for Server, put m.google.com if google. this way, all gmail contacts will show up in iPhone (they won't if you add it as Gmail). i am thinking that all those contacts, calendars, emails, etc. on your devices will be saved into iCloud, but i don't know how to check that. i got all mine.