I have been using Gmail since its early invite-only beta days in 2004. As explained by Google, they were involved in a dispute over the use of the Gmail name in the UK, so they were forced to rebrand the UK service to Google Mail in 2005. Existing UK users were allowed to keep their @gmail.com address (although the logo on the Gmail interface switched to the new Google Mail logo), while any new customers were assigned a @googlemail.com address.
Fast forward to today and it appears that Google have reached a settlement, as they have rebranded back to Gmail in the UK. Effective immediately, new UK users will again be able to sign up for @gmail.com addresses, while existing users will be able to choose whether to switch or to keep their old @googlemail.com addresses. The Google Mail logo will also be phased out and replaced with the Gmail logo.
This doesn’t really mean much in the grand scheme of things, as whether the “official” email address (as displayed in the Gmail user interface and in the From field of all sent emails) is @gmail.com or @googlemail.com, the domains are actually interchangeable, but it’s still a good step forward which will eliminate a lot confusion.
The only country in which the Google Mail brand now exists is Germany, where there is an ongoing dispute between Google and the owners of German company G-Mail. Maybe Google will now look to resolve this and be able to offer Gmail as a truly global brand.