I have used them a lot! When I'm in new areas and think I can shorten the trip I tend to find out the map was smart.
You can view the bike routes on the map
too by right clicking over the map and selecting "Google Bike Routes".
- best in cities of course
With the red crosshair in the center of the map you can also right click and do direction "from" and "to" anywhere regardless of the bike layer.
Then when the directions pop up in the left pane select "Mode of Travel: bicycling"
Now for the cool part, at the bottom click "Edit" to send to "Route MGR" or directly download and put it in your GPS
Of course most use smartphones for that now so it's easier than ever without needing a gps unit since you'll probably be in cell range.