There is a long, easy to read 10 year retrospective of the Chernobyl accident here:

The short answer: It was bad, very very bad.
But it was not as bad as we thought it would be over the long term.

Keep this in mind as we look to Japan. A reactor with a better design by GE, a better safety system all around, and "total failure mode" for these plant (a full meltdown and core rupture) would not be as bad as Chernobyl in terms of hard gamma radiation exposure to the environment and Iodine 131 and Cesium contamination.

Of course, THREE nuke plants having total failure will affect a massive number of people - the majority of whom have already been evacuated.

There may be no "coming home" for 250,000 or more people here.