A funny thing happened to me a couple of days ago when I completed my move to WordPress by deleting Enter Content Here from Blogger. The old RSS feed (http://contenthere.blogspot.com/feeds/posts/default), which FeedBurner somehow kept alive with new content posted on WordPress, suddenly went dark. The net result was that I lost my first 300 (or so) subscribers. To them, I stopped blogging after my eZ Publish Fork post on February 25th. Hopefully, these subscribers will notice the fetch errors and repoint to http://feedproxy.google.com/EnterContentHere (please spread the word).
What took me off guard was that the old RSS feed was being updated by the new site rather than the old site. I think this is because I elected to "merge my feeds" (or something like that) when Google bought FeedBurner. The readers who were subscribed to my old blogspot feed didn't notice my warning posts and the fact that I made the old blog look really ugly by changing the template. They saw the new posts and clicked through to the new blog.
So, if you are thinking about moving off of Blogger, first read this post. Then, if you merged your feeds, remember to put a couple of warning posts on your new blog to let people know you are moving before you delete your old Blogger blog.