here is how to login to iCloud even if you are not a developer or a previous MobileMe user
Prerequisites:
Mac OSX Lion 7.2 with iCloud Beta 5 installed
an iOS device, iPad or iPhone
1. Setup "Find my iPhone" on your iOS device using your Apple ID
2. On your Mac, setup an iCloud account using the same Apple ID. (it's under Mail, Contacts and Calendars)
3. When complete, try logging in at icloud.com
You can also "reserve" your me.com email address
When setting up the iCloud account on your Mac, select Mail & Notes.
You will be prompted to choose an email address
Just enter the email address of your choice and it's done.
You won't be prompted to choose a password for the me.com email address;
it's tied to your Apple ID.
Try sending a test email to your me.com account.
Now open your Mail.app; it's automatically configured