I spent a week in Perth and the surrounding area some 2 or so years ago and really enjoyed it. Headed down to the Margaret River region and daytripped as far south as Walpole and the beaches on the south coast. The region is great for forest scenery (including a good canopy walk) and great coastal views and beaches without that many people around. Also all the wines if you're into that. Driving distances can be substantial and it's hard to forget returning late one night across some distance and trying to dodge the kangaroos. Small towns have a certain charm but close down early. Perth itself is pleasant but didn't have a lot that I thought was world-class about it; am sure Melbourne or Sydney would run circles around it for urban attractions.
A good commercial for Western Australia might be looking at some of the photographs of Christian Fletcher at
www.christianfletcher.com.au