Blojsom uses the Atom API – which has caused a huge divide in the community. Alongside the older blogger and metaweblog API's. So its pretty much forward looking. I havent spent enough time looking at it but there seems to be a few good applications already, even if there only demos.
People have started writing plugins – Yeah its not exactly the moveabletype community but you know what its the start of things? By the way, has every mac user gone nuts for ecto? And I need to try out NetNewsWire's Atom beta.