We hope you didn't get too attached to Outlook.com Premium -- from all indications, it's already going away. Microsoft is adding most of Premium's features (tougher email security, ad-free web access, more storage and top-tier support) to Office 365, but in the process has revealed that it's removing the paid option for Outlook.com users. You can keep receiving the benefits if you renew an existing subscription, but new subscriptions are "closed." If you took advantage of the custom email domain, which isn't coming to Office 365, Microsoft is working on a way to transfer that domain somewhere else.
If you still want Premium's perks, you'll need to have an Office 365 subscription linked to one of Microsoft's email domains, whether it's Outlook.com, Hotmail, Live.com or MSN. You may also have to be patient, as the the features will take "several weeks" to roll out to Office 365 Home and Personal customers.
We've asked Microsoft if it can elaborate on the decision to cut Outlook.com Premium and will let you know what it says. Whatever the motivation, it's clear that Microsoft is putting a lot of stock in Office 365 -- the productivity service just became that much more tempting, even if it's at the expense of another offering.