They did a bunch of them near where I used to live. The problem with these (and really all unplanned high density housing) is that while their intent is to create walkable communities (a great idea in itself), they ignore the reality that most people are going to commute to a job, and they create the nastiest traffic bottlenecks ever. They're not bad when they're located next to a major highway with preplanned egress/ingress, but many of these halfwit developers will plop them with an entrance exit on an already busy 4 lane road and wonder why everything is all wacko.