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We present a detailed measurement of the proper motion of the Crab pulsar,with the primary goal of comparing the direction of its proper motion with theprojected axis of its pulsar wind nebula (the projected spin axis of thepulsar). We demonstrate that our measurement is robust and has an uncertaintyof only +/-0.4 mas/yr on each component of the proper motion. We find mu_alpha= -11.7+/-0.4+/-0.5 mas/yr and mu_delta = +4.2+/-0.4+/-0.5 mas/yr relative tothe pulsar's standard of rest, where the two uncertainties are from themeasurement and the ncertainties in correcting the proper motion referenceframe, respectively. Comparing this proper motion to the symmetry axis of thepulsar wind nebula, we must also consider the unknown velocity of the pulsar'sprogenitor (assumed to be ~10 km/s), and hence add an additional uncertainty of+/-2 mas/yr to each component of the proper motion, although this could besignificantly larger. This implies a projected misalignment with the nebularaxis of 14+/-2+/-9 degrees. We conclude that the precision of individualmeasurements which compare the direction of motion of a neutron star to a fixedaxis will often be limited by fundamental uncertainties regarding referenceframes and progenitor properties. The question of spin-kick (mis)alignment, andits implications for asymmetries and other processes during supernovacore-collapse, is best approached by considering a statistical ensemble of suchmeasurements, rather than detailed studies of individual sources. [abriged]

A Precise Proper Motion for the Crab Pulsar, and the Difficulty of Testing Spin-Kick Alignment for Young Neutron Stars