I've changed hosts and it never affected my PR. I even had a site offline for a month, and the PR was still there when I got it back up.
It can affect you in a lot of ways (such as engine rankings). Be careful and follow Matt Cutts instructions to move to a new host without being affected. http://www.mattcutts.com/blog/moving-to-a-new-web-host/
The change of host won't have any effect on your site's PR. When you start losing inbound links, your site's PR could fall.
Like everyone said, PR is based on your domain name. So as long as your domain name is staying the same, you should be able to move your site to whichever host you want.
To me that just looked like a " how to " change hosts Anyhow , I just moved a HUGE site to a different host and all my results , and pr are fine