Yes, we love Atom, too. :)
For the past couple weeks, we've been working full-time on implementing the RSS platform features in Longhorn. Of the many interesting features the development team has been checking in, I thought this one might be found interesting: last week, Atom support was checked in by John Lueders (one of the developers on the team). That's both 0.3 and 1.0 (based on the -09 spec) support.
That check-in completes Longhorn support for the different syndication formats. The grand total is: RSS 0.9x, RSS 1.0, RSS 2.0, Atom 0.3 and Atom 1.0.
However, just to set expectations, we locked down on Beta 1 of Longhorn about a month ago, so the release of Longhorn that will be public soon won't have Atom support, but the bits we'll have at PDC in September, and in Beta 2 will have it.