It appears all is not well with the iCloud servers today. I've been unable to retreive my email for a couple of hours now. All the other iCloud services seem to be working though I've been stuck trying to open the web mail app for the past half-hour or so. Back with more later...
UPDATE 15:10 CDT: Mail appears to be working again (although a bit slowly). On occasion my Mac asks me for my password again, even though I keep it in my keychain. Things are definitely not up to snuff, but at least it's working now.
I really can't complain. I transitioned myself and two daughters over from MobileMe without a hitch. I'm hearing others weren't so fortunate. Today's uh-oh is the first we've experienced. If this is the worst that happens, I'll count myself lucky.