If you want it to fall away in a specific direction, select an option from collapse type in the attribute panel for explosion.
Gravity will explode and then drop downwards gradually.
Random will go all over and ascending/descending goes up and down.
There's also the movement type which decides where the shrapnel goes (or what point of the text will explode first and which is last) and action sequence which you can experiment with for the best effect.
When experimenting, I'd advice using 320x240 project setting and curve quality as draft.
This will render much faster and then just set the curve and output quality to the desired level when you are happy with it and want to render the full project.
With the explosion option, you can mess with the timeline and set different levels which can give you a full-on quick explosion to a gradual or even a matrix style slomo.
Here are two early drafts I did using this effect:
http://www.re-volutionmedia.com/logo.wmv
http://www.re-volutionmedia.com/logo1.avi
You can really jazz things up with the particle effects using fire and smoke.