You have to provide your gmail address when you first boot-up Android. Would this also work with, besides from @gmail.com addresses, e-mail addresses from your own (sub)domain that are being hosted with Google Apps? What I'm talking about is the possibility here to let Google host Google services, such as Gmail, on your own domain name. You would have a firstname.lastname@example.org address, but it would be Gmail technically.
Would this work for the initial Android set-up? Has anybody tried this? It might give you more freedom later on if you decide to abandon Gmail and let someone else host the mailboxes. It might even make Android accept non-Gmail addresses in that way (allthough the contacts and Gmail app etc. services would likely stop working).