Go-via was not around when I got my tag. It seems video matching fees may apply in some places, so depends where you are going.
If you want a tag you can get one through the RTA NSW website (or that go-via one). There was a deposit when I got mine bu, no ongoing account fees and you can set up automatic payment top ups. You register up to 5 (I think) vehicles for the tag. It will work on all the Australian toll roads (NSW, Vic and Qld) I have my car, the ST and the wifes car on it. As I don't go on those roads that often the cost does not worry me, particulary if I just want to get through Sydney from the ACT going north or just get into the centre of Sydney. I usually use the ring road in Melbourne so tolls are not an issue.