Looks like it. You can't access the main MobileMe page. Apple says this on their MobileMe support page:" MobileMe members are intermittently unable to access MobileMe services. Mail is available via a desktop email application, or Mail on iPhone or iPod touch. Normal service will be restored ASAP. We apologize for any inconvenience."
Well, at least that page is up. Seems like MobileMe has had a rough couple of weeks with issues concerning mail, Back to my Mac, and syncing.
The MobileMe service had a rocky start and has had a variety of issues over the last year or so. Let's hope Apple gets things back on an even keel soon. So far this morning, MobileMe is MobileGone.
UPDATE: Some of us are able to log in, but it has been up or down for various people throughout the morning. The status page still says the issue is intermittent as of 3:15pm ET.
UPDATE #2: Looks like everything is back to normal. Thanks to everyone who sent this in!