  We provide a critical perspective on the collection of low-temperature
transport phenomena in low-density two-dimensional semiconductor systems often
referred to as the 2D metal-insulator transition. We discuss the physical
mechanisms underlying the anomalous behavior of the two-dimensional effective
metallic phase and the metal-insulator transition itself. We argue that a key
feature of the 2D MIT physics is the long-range bare Coulombic disorder arising
from the random distribution of charged impurities in the low-density 2D
semiconductor structures.
