It is tested with gmail and works fine, email id length is not an issue.
It is not expected to replace everyday email but to be used in cases where you do not want to share your actual email id.
Also in many cases the email id of a user is not known and only bitcoin address is known this can be useful in that case. Eg: You received bitcoins from some address and you want to send a message to the person, it can be used in that case.
Exactly, the idea is good for certain use cases, as long as the e-mail provider supports case-sensitive local-part e-mail addresses.