We've been giving you warnings. The signs have been there. Preparations have been made. Now, it's time!
That's right, it's time to embrace the new version of Blogger! Starting today, a small percentage of users who log in to an old Blogger account will be required to move to the new version. This involves moving your current Blogger account to a new or existing Google Account. After the move, you will need to log in to Blogger with your Google Account username, which is always the email address associated with your account. If you're one of the lucky folks who is prompted to move your account over to the new version of Blogger, you'll be able to postpone this process once (and only once) if you *really* need to get a post out of your head or want to say goodbye to the old Blogger. After that, it's time to befriend the new Blogger!
I really don't understand why Blogger team needs to make a big deal out of this switch. When Writely became a part of Google Docs & Spreadsheets, nobody asked Writely users if they want a completely new interface, a new name for the application or the integration with Google Spreadsheets. Google redirected writely.com to docs.google.com and that was all. Blogger could have switched the accounts automatically, as the new version is backwards-compatible and the visible differences aren't significant.