Well, the problems aren't with Atom so much as with Blogger's implementation. First of all, what's with this thing:
That might be OK in a beta test version, but who wants that to show up whenever anyone syndicates your site? I've tested this from several other sites and it's always there. It doesn't necessarily show up with aggregators, but it does if another site pulls in your feed. Very unprofessional looking and pointless to boot.
Secondly, where are the links to the full post? Obviously if you have your settings to show partial blogs, you want the reader to be able to jump to the full post. Except for aggregators, I don't see where links are provided in Blogger's implementation of Atom.