Currently planning a trip with a mate.
I have done bits and pieces in several sections in the last few years.
"Doing bits and pieces" = scrambling about in thick scrub and lawyer vine looking for the damn thing. I have found clear parts/evidence of the track but (without having comparative experience from the past) my feeling is its a lot more difficult than it used to be.
Anyone i've talked to who's done it recently says it's *&%$#!. But i'm keen to give it a go. I know various exit points if its getting painful... and some of my sorties have been pretty painful so i know what i'm in for.
Edit: have I seen remnants of the track along the lower part - yes, I think so. Largely stone work propping up a bit of a pad. I couldn't tell you exactly where though (although above burralow creek sounds right). In the upper part, the same - there's a nice couple of bits below the darling causeway and under Ikara head that are quite obvious (and then suddenly, absolutely nothing at all and the worst lawyer vine I've encountered more or less). Then the whole section from Burra Korain -> Blue Gum Forest follows where the track was, as well, and is is common use, i.e., it is still the track; you can still see remnants, perhaps, but, because it's been in use for a long tim, how much is actually what the engineers did and how much has been fixed/reconstructed/looped over etc etc is anyone's guess I suppose. In the middle section, the bits and pieces I've looked at, under faulckonbridge and linden, yeah, not much.
Edit 2: had a look through some old pics. The only ones I could find was the section under Ikara ridge up near the top:

And here's me trying to recreate a photo taken on the track in the 1870s with Ikara head in the background (no top hat and tails for me I'm afraid)


Couple of things worth noting - there's a famous story of a couple of Tiger Walkers from the Sydney Bushwalkers running it from Blue Gum -> Yarramundi in 20 hours - I think Max Gentle and the other being Dot English/Butler who did it in her classic barefoot style. Can't talk about the track/route without mentioning that.
Also, as alluded to already, it was never going to work as a route for the railway - I seem to remember that the fella(s) in charge were well aware of that after not very much time at all, but had their contract for the bridal trail and pushed on none-the-less.it was completed though, all the way to the Hartley Vale siding on the darling causeway.