This is a weird move. Why would Blogger-Google do this? Most every XML syndication tool supports RSS and more dont support Atom than do. Further, Atom isn't even stable and will change considerably before its final release. Both of their largest rivals, Yahoo and M$FT are putting bucks behind RSS. Could it be that Google is putting its cards on the table? Is the syndication war being taken over by the big-wigs? M$FT. IBM. Google. Yahoo. Move over Userland and Six Apart? Told u so.
So what now? If you don't like what Google is doing w/ Atom-RSS, then send them a message and stop using their search engine. Mind u, iM not there.