We did this trip April this year. The road from Broken Hill to Packsaddles is sealed all the way and is a good road. From there to Toboburra is is sealed in places, but some of the places that are unsealed are very corrugated, and some bad bits appear very suddenly. The short diversion into Milparinga is an ok gravel road. The road out to The Corner is quite a good road, except for the last 20 odd km, very rough. We were informed the other road (to the north), is a rougher rlad in general. 

But it is an enjoyable trip and worth doing.

But phone Packsaddle and Tibooburra before you go to check on the roads. Dont listen to Btoken Hill Info centre, as they have given us the incorrect info on a couple of instances.