As train services go Countrylink Southern Explorer is pretty mediocre. It's more expensive than a Sydney-Canberra coach ($54 vs ~$30ish) but also a leisurely hour slower. Be aware that it arrives in Fyshwich, the ass-end of Canberra, and there isn't any public transport after 7 on weekends or 10 on weekdays. So probably avoid trains after 6pm.
Breakdowns mustn't be that rare either because because between the above reviewer and I, we've seen it breakdown it twice. They were quick with the replacement coaches but you're probably better off just catching a coach in the first place.
Seats were seats, air conditioning worked while the train was still running and the food was ok. read more