I have found that you can expedite map updates by zooming out, let the map refresh (3 to 5 seconds) then zoom back in again to the same spot will provide a faster update of the surrounding wazers. I find a lot of times wazers will just disappear off of the map. Doing this process expedites a map refresh. I'm assuming that this works because your just checking the database more often.
Doing this process you get an update in around 10 to 15 seconds instead of minutes.
It helps when all friends are descending on a single spot from different locations (and you have nothing better to do but just wait ...).
Obviously you wouldn't do this while driving.