PRO is feed analytics taken to the next level. You will now have access to the number of people who have viewed or clicked individual content items in your feed and “Reach,” which estimates the daily number of subscribers who interacted with your feed content. You can turn this on by signing in to your account, navigating to the Analyze tab and heading to the FeedBurner Stats PRO section. Click the "Item Views" checkbox to activate these PRO features.
The MyBrand service (also PRO-level) is located under the "My Account" tab after you've signed in. MyBrand lets you maintain consistency between your feed address and your hosted website's domain, if matchy-matchy is your thing. For example, rather than using feeds.feedburner.com/MyFeedName, your MyBrand-ed feed address can be feeds.myexcellentdomain.net/MyFeedName. To get started with MyBrand, sign into FeedBurner, click the "My Account" link in the upper left-hand corner, and then click "MyBrand". Nota Bene: You must be comfortable playing around with DNS entries and own the rights to the domain whose DNS entries you'll be playing around with in order to successfully activate MyBrand.
And if you have been paying for those features, feel better! you will not be charged for the month of June 2007 and beyond.