Sure, you can use MapQuest to find the fastest driving route from the casino in Atlantic City to the poorhouse on Baltic Ave. But can you find the fastest transit-based route across Eugene, OR? Yes, with Google Transit you can. I know that many will complain since our major cities (NY, Philly, DC) aren't included. But play around with Seattle (which has a pretty dense transit infrastructure) and you can see the potential.
When this thing learns to help you jump from city to city (even within a region) it could really start to get some people riding the rails. For my geomatics students, what sort of information do you think is required to make this thing work? What do you imagine the algorithm looks like?