Courtney's thread is accurate for intercity transit and the density of her region. However, I think that areas that already have sufficient housing density should invest heavily in buses now, and not wait for trains. Like, say, a certain cluster of three cities in Eastern PA.
Here is my pitch for anyone who has worries about rail: I think that building out rail is a necessary (but not sufficient) step in transforming American cities from totally car dependent to slightly walkable, in a way that no other form of transit is.