How safe is an open WIFI network?

I local pub where I hang out at has free wifi access but it is over an unsecured network. How big of a risk am I taking by using it? I'm not doing any online banking or using paypal from there. Should I be worried about checking my email?

 

Funny you should ask-- they've been playing this all day on CNN:

http://www.cnn.com/2005/TECH/internet/06/21/hotspot.hacking/index.html

 

There are two issues involved.

One is the interception of you actual activities (which you seem to have under partial control).

The second one is more crucial; depending on how you Sharing are configured others on the same Network might have an access to your files.

 

Since you're not hosting the wifi network you're not at high risk. But open networks don't use mac-filters or wep keys (unless provided of course) so if anyone wants to abuse that you are an easy target.
The risk you take rests solely on the provider of that acces point.
Be sure however to disable any shared documents etc.