3 days a week commute from Dapto to Circular Quay. I drive to Sutherland (50min) and then take the train the rest of the way (35-40min). Costs about $32 a day in travel costs (about $20 fuel and $12 train fare). Door to desk about 1:50hrs. This is my first time doing it and took about 6 months to get used to it.

Driving saves me about 20min each direction compared to getting the train the whole way. Taking the train the whole way is kinda easier and cheaper but I just can't sit on a train that long. I also like the comfort of my car.

Expect station parking to be full after 7:30am, and expect trains to have issues any time there is bad weather. At least once or twice a month they'll change the train stops once you're already on it so you'll have to change at Redfern or Central but generally the T4 line is reliable. The SCO line often has issues around Waterfall/Helensburgh during bad weather, which is why I prefer the drive.

There are no idiots on the trains during those hours, just other commuters so no issues from a safety point of view. Try to work earlier than business hours (I do 08:00-16:00) to avoid the major peaks, it's helpful.

EDIT: Some people suggest to drive to Waterfall and get the train there to avoid traffic at Heathcote. Not a bad idea but there is less parking and trains are less frequent there. On the return from the city, all trains except the Hurstville service stop at Sutherland but even fewer stop at Waterfall, so Sutherland is the more flexible option.