I used the section from the city centre to Dalmarnock Road when I lived in Rutherglen, it was fine apart from the stink from the sewage works. As with any path alongside a waterway in central Scotland, you come across loads of alcoholic bampot fishermen, but never had any bother.
You could come off onto Dalmarnock Road and take the main road (or cut through the industrial estate on the left before the big Tesco) along to Cambuslang then rejoin NCR75 just after the Cambuslang shops – that would avoid the Parkhead/Springfield Road bit, which I'd hesitate to ride along as well. Not sure what the cycle path's like after that. I've ridden along the road that goes through Halfway and out to Hamilton via Blantyre a few times, its not that bad and pretty direct.
Take it you're doing this on a road bike of some sort?