There are several people who are complaining that Google Maps is incredibly slow for them. If you have slowness issues with Google Maps, you may be in luck. A Google Maps Help thread has a Googler helping these users by troubleshooting issues with them.
Googler, Mike CH, believes there are certain firewalls that may be causing the issue. There seem to be two issues, the first is loading the map tiles and the second is trouble loading the JavaScript "brain" of the site.
Mike is asking these users to run traceroutes and disable their firewalls. If you are also having issues with Google Maps, you may want to participate in the thread.
Forum discussion at Google Maps Help.
