I had a bit of an interesting experience last night about ADSB...
I already was 90% ADSB ready, so when my last transponder blew, I replaced it with a GTX330ES (thanks Jaba!) and boom, I was ADSB compliant, so it didn't cost me anywhere near where a lot of these figures are coming from, and, I didn't even require an EO, but that's another story...
Anyway, it was after midnight, going Rocky to Townsville at 8500 and I there was nothing happening and I asked BNE center how my ADSB was on their end. What followed was, that he couldn't see me that low anywhere basically between 130nm south of Rocky up to Horn Island. I asked if ducking up to FL125 would have done the trick, but he said no. There is basically no ADSB coverage from near Gladstone up to the top of Queensland, around the coast and inland quite a bit for "low level"! It did make me wonder why we are rushing the install when there are huge coverage gaps?