... I hear the Sony DSLR forum regards them as the spawn of hell, for example.
eh??? The Minolta Dynax/Maxxum mount (which is the Sony a-mount) easily takes M42 lenses with a glassless adapter - with no infinity focus problems. Dunno where you got that info from. There's a whole subforum on Dyxum.com dedicated to M42.
Mamiya 645 Super | Nikon F4/F100 | Minolta Maxxum 9/Dynax 7/X-700/X-500/XD7/SRT-101 | Pentax Spotmatic | Canonet QL 19 (GII) | and a whole bunch of glass