I just noticed this now! - but feel compelled to reply - I own a CS70M and several fully operational CS80s.
The CS70M is worth purchasing. It is definitely not a CS80, but that's not a disadvantave - it's just a different instrument.
The CS70M is not an instant machine. By that I mean that it does not instantly gratify, but with time, it really shows that it has character. As you get to know it, it reveals two exquisite qualities - the same 'CS' analog sound as ALL of the vintage CS range and with the advantage of (monophonic) aftertouch; and, when placed with a modern effects, it can be truly immense - I mean 'really' massive.
Because its a dual channel synth, you can layer two sounds and create massive textures that are either layered similar sounds , or contrasting sounds.
So overall, if you realise that its not a minimoog or a CS80, you'll get a synth that deliver its own character.
It suffered becasue it came in the wake of the CS80 and just before the DX7 - it never had a chance - but it is an intstrument with its own substantial character.