Hey mate, there are plenty of options out there with many people saying the one they use is the best one. I recently purchased the Hema 4wd maps for iPad and took it on a 1 day trip out of Sydney a couple of weeks ago. Very easy to use but not super detailed for the area we went. I think it's more suited to the touring and iconic trips, and I'll have more info on this in a few weeks when I get back from a high country trip.
I also have a Garmin 62s for its portability but use it on the dash as well. The standard Garmin maps go well but you can also use Oztopo maps (for a cost) that also work quite well from what I hear.