I've traveled that route, (well, as far as Walgett) on my way home from Townsville via Dubbo and found the road to be in mostly good condition apart from quite a bit of roadworks going on...mind you this was probably 6-7 years ago so hopefully the roadworks have been completed by now...
Also, from memory quite a few trucks use that route...with a number of road trains heading back & forth from Charters Towers.
It's also a fair hike from Charters Towers to Clermont...something like 350k's??? with just a road house roughly halfway between.
If you're happy to do a 1000k day, I find Roma is a good place to stop for the night.
Cheers :)