Migrating FeedBurner to Google Accounts hasn't been a smooth process and the new FeedBurner doesn't look very promising. Last month, Google officially launched AdSense for Feeds and asked those who want to join the program to "burn" their feeds using FeedBurner. If you were already using FeedBurner, Google provided an email address where you could contact a Google employee to manually migrate your account (since then, the email address has been replaced by a form).
After a day or two, FeedBurner's new home at feedburner.google.com finally allowed you to log in. Some people found that the number of subscribers dropped to 0, but the most visible changes were the features which have been removed. The Googlified FeedBurner no longer includes web stats probably because of the overlap with Google Analytics, the feed stats history isn't available and you can no longer manage the list of email subscribers.
Another strange issue is that Google Blog Search stopped indexing this blog and many other blogs after migrating to the new FeedBurner. There are many other bugs related to this transition, but FeedBurner failed to acknowledge them.
Update. In about 2 weeks, Google has addressed some of the issues:
* Blog Search indexes feeds
* you can manage the list of email subscribers (there's even a new option to filter that list)
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