I've now owned 5-6 different Spotmatic bodies over the past few years with most being from thrift stores, and some being hand-me-downs/gifts. They've all been accurate enough to run slides through, and have matched my EOS 3/DSLR bodies meters close enough to not be an issue. I'd recommend them but only if you are comfortable reducing flare in your own technique/methodology. The lenses you can run are definitely not up to modern standards if you don't know some techniques to help out.
The longer lenses are definitely not up to modern standards in IQ either.