SYD/YYZ,
Access to the Golden Lounge in the Sat terminal is a great benefit of MH J tickets.
This is a very spacious lounge, with plenty of lounges, a few with power outlets handy and a large central kitchen/bench island, acting as a room divider, with food and drinks on either side.

The business centre has some (very old!) terminals and a printer if you need it.
I ordered some dishes during our stay, from the chef's counter, as well as picking from the self-serve bars.

There are massage therapists and cubicles (for a small fee) toward the rear of the lounge there if you are into that.

I didn't try the showers but would be interested to read about your experience as I'd like to do a SYD-KUL trip like yours and use the lounge next time, instead of the transit hotel which we used last time.