Hopefully there will be no squashing. The Spotmatics are very nice, though they use the old screw mount which is technically 'obsolete'. You can still use M42 lenses on modern Pentax, Canon or Minolta/Sony AF SLRs or dSLRs with the right adapter, though obviously no new lenses will work on the old camera. It might be better to start with something that uses a current mount (Canon EF, Pentax K, Nikon F, or Minolta/Sony A) as this way you will be able to use the lenses on both a film SLR and also a digital SLR if or when you get one. Of course this is just a matter of preference; a manual-focus-only M42, Canon FD, Minolta MD or Olympus OM system or any of the many other 'obsolete' systems would also be good and possibly excellent value.
By the way, are we definitely talking about a film SLR? I notice the OP only mentioned digital photography.
By the way, are we definitely talking about a film SLR? I notice the OP only mentioned digital photography.