The Issue of Nader in 2004
It's a no-brainer, even though it is tough to not vote your conscience wholeheartedly. Here is a sampling of the left blogosphere opinions:
Tbagged on The Great Nader Debate
The Leiter Report: Nader Shouldn't Run in 2004
From Talking Points (no title)
One of the most thoughtful and thorough is from the strangely organised The Progressive Southerner, from May 2003.
Also in Salon.com (you have to watch an ad to read it, but they're usually pretty good.)