My main conclusion is that the accreting black hole hypothesis seems fully capable of accounting for the quantity and characteristics of the radiative output from quasars, and is the type of model on which fuller work would seem most worthwhile. At the moment, it provides a promising general "scenario" for interpreting the data and for suggesting areas for worthwhile theoretical investigation: it does not yet constitute a precise model that can be directly confronted with observation. Further work could make the hypothesis more specific, but the quasar phenomenon is probably too complex ever to be explained by a straightforward few-parameter scheme: not only is the geometrical configuration uncertain (and unlikely to be either stable, homogeneous or isotropic), but the observed features depend on the angular momentum, magnetic flux and history of the infalling material, as well as (of course) on Mh and M. More generally, it would still seem worthwhile to investigate all aspects of the interaction of stars and gas in a relativistically deep potential well (c.f. Fig. 1), with the eventual aim of interpreting some forms of activity of galactic nuclei as an evolutionary sequence.
Figure 1. "Flow diagram" indicating the processes whereby a massive black hole could form in a galactic nucleus. Quasars can be interpreted in terms of accretion of gas (or even entire stars) onto a black hole of 107-108 M; and some of the less violent phenomena observed in the nuclei of galaxies may represent "precursor" stages.