(btw, I enabled titles in my blog. There is still no way to transmit titles over the Internet, but you can post them manually. It's a learning process for us all).
So NetNewsWire doesn't support Atom directly in any released version. I found this beta version that adds support for Atom. It's apparently a pre-release of 1.1.
Update: The next release of NNW will indeed support Atom and the release should should be a lot bigger than the 1.0.9 tag the release linked to above has (or the 1.1 tag that the page also talks about). I know how long it takes to get releases right, so more power to them.