The existence of a rapidly spinning, magnetized, neutron star at the center of the Crab Nebula is revealed in the soft X-ray band both by the pulsed point source coincident with the pulsar and through the strong, diffuse, synchrotron emission of the nebula itself. Recent Einstein observations have shown that in three other cases (Vela, 3C58, and CTB80), point plus extended Crab-like emission is associated with putative young neutron stars in supernova remnants. In addition, we have recently discovered evidence for point and extended X-ray emission from older, isolated radio pulsars. However, for the majority of young SNR, no such emission is observed. Since any synchrotron nebula emission is presumably isotropic and depends only on the ambient magnetic field strength and the energy-loss rate of the central neutron star, we can use these data to set stringent limits on the initial spin periods, magnetic fields, and/or the existence of young pulsars in historical SNR. The implication of these results for Crab-like remnant evolution and neutron star production will be discussed.