As an every day commuter I am really happy to see this happening. The bike directions take a lot of factors into consideration:
designated bike lanes, tries to avoid areas with lots of hill climbs and drops, busy roads and intersections. In giving estimates on trip times, Google uses an average person at an average Body Mass Index level, peddling up and down the terrain. Let’s take a look at my usual morning route. I checked it with GPS logger and it is 9 miles which takes me about 35 minutes. According to Google Maps it is 11.6 mi and takes 1 hour. This feature is still in beta so I hope they will make some improvements 
