what are the benefits of using the @icloud.com email address?

There's no benefit at all. You don't have to use your new @icloud.com address if you don't want to.

It's purely there as an optional, additional address you can use or ignore as you wish. Obviously, now the service is called "iCloud" it makes sense to offer @icloud.com email addresses.

Some people didn't like the @me.com address, now they can use @icloud.com if they want.

my ID can't enter anything Mac store, appstore, itunes, imessage, ichat, icloud

I tried by using @gmail @me @icloud not work .

also reset my password .. said the message is sent but I didn't find any message in e-mail

and Ican't enter to @icloud @me mail ,but enter to @gmail

when i choose (Answer security questions) and wrote my answers said your birthday is incorrect ?

By find My Apple ID the same problem

may be apple message can't arrived to my mail , because security settings??? And solution

Or Someone rabbed my ID ?????/