Is iCloud space based on your account and shared between all your apps, or a separate allocation by device? (i.e. My free allocation is used up by my iPhone, will there be no space left for the iPad?)
It still REALLY irritates me that I have one user id (tpr007) for my iTunes account, and needed to create a new one for iCloud. It's so disjointed :
As far as I'm aware, you have to use an email address as your ID for iCloud.
My apple ID, which I've used to buy lots of apps with, is just a one word username.
I think you have to convert the old style of apple id (one word username) to your email address before it will work.
I had to do so in order to use Find My iPhone a while back (before iCloud)