Today's NPR story about home prices dropping everywhere except near transit lines seems to argue that availability of transit options is maintaining home prices in many areas. This may be true to a point, but I think an equally relevant question is whether "driving until you qualify" simply got a lot of people into homes that they couldn't afford. It's one thing to drive until you qualify for a mortgage that fits your budget, but quite another to drive until you qualify for one with crazy terms. In addition, many of the new construction homes were bid up by small time (and short term) investors, not actual long term homeowners.
I certainly see the advantage of living near transportation options, and I expect that as prices decline more attractive areas (because of amenities or transport choices) will hold their value better. But I don't think the availability of transit is enough to stop the overall price declines.