iOS Simulator - Can't log in with iCloud

TL;TR Log into http://www.icloud.com and agree to the terms.

It works. But there are some additional steps needed:

At work I tried with my new apple id: at work XYZ@mywork.com. At first It didn't work even though I was able to access iOS dev center. I realised that it is required to access to http://www.icloud.com with such Apple ID and agree to the terms. After a few seconds I received a 'Welcome to iCloud' email to my work address and then I went back to the simulator and I successfully logged in.

BTW, for a personal account XYZ@mac.com I have for ages and use regularly it worked from the beginning probably because I have agreed to the terms a long time ago.

So not only @icloud.com of @me.com or @mac.com accounts work. All accounts work.

1. Create an Apple ID from appleid.apple.com. You need an email address and a phone number to authenticate.

2. Login to icloud.com and accept terms and conditions.

3. Open Simulator, log in with your new Apple ID.

4. Done.

I had the same problem today as I was trying to use iCloud + Core Data in the simulator (iOS 8.0, Mavericks). What I found out is that you should use, in the simulator, your @icloud.com e-mail. If you do that, you are able to login and use some iCloud functionality.