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Graham, by all accounts given its heritage it’s a formidable sensor.
Regarding the gain reference...the ZWO drivers implement gain in 0.1dB steps, so a gain increase of 10 is 1dB, increase of 60 is (importantly) doubling the gain....which, not completely by coincidence, is the same as increasing the ISO on a DSLR by one stop, i.e. going from ISO 800 to 1600. That’s it!
Unity gain is only special in that it represents the gain value where 1 photon results in 1 electron. It may not necessarily be the best gain to use...depending on the sensor, the best gain value is a balance between dynamic range, read noise and exposure time. The same is true for a DSLR.
Really, the only difference between traditional CCDs and the new crop of CMOS sensors - from a using point of view - is the concept of this changeable gain, that many CCDs don’t have. What gain to use is as much a question of taste/priorities, within certain limits.
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