I normally do the trek once or twice a year and usually just suffer bad coffee or go without. To my knowledge theres no place that is exceptional enough to warrant a stop; and certainly some of the coffee making practices Ive seen whilst eating have made my eyes pop out.
Theres one place in Holbrook that claims to have the best coffee on the hume. Black signs for miles before you reach town. It might be worth a try, though I keep driving now.
You can read about Andys drive to Sydney here: http://coffeesnobs.com.au/YaBB.pl?num=1238074452/0