While I've been a pretty loyal NetNewsWire/NewsGator Online user, I can definitely appreciate the power that the new Google Reader is throwing down. It's so good, I'm going to give Google Reader a week to cure me of my NNW addiction.
For those of you who have already made the Google Reader conversion (a la Merrin), then let me recommend GROSX, an OS X app that lets you know when you have new feed items in Google Reader. GROSX brings Growl functionality to Google Reader and can be your default news reader in Safari or Firefox. Eli has more GROSX tips at his blog.