I have identified a workaround for the lagging-display bug
(follow the trail of links for description & history) that I have been experiencing & profiling since the pre-3.0 betas.
When the client is stuck as per this bug, turning off the phone's display or
switching to a different app will allow the pending routing request to go through normally. (If you turn the display off, Waze will sometimes reactivate the display once it "wakes up" with the route.) So while I'm driving, if I leave the chosen route for some reason and it starts to recalculate, all I have to do is turn off the display, and it will come back with the new route in just a few seconds.
If you have experienced this problem, please report if this workaround is effective for you.