I spent a week in Perth. I enjoyed it very much. It is a very much 'outdoors' place.

I spent a day on Rottnest Island riding bikes.
I took a fun all day tour up to Lancelin Dunes and Pinnacles National Park. It was great to get out into the remote part north or Perth along the Indian Ocean.
I spent a Saturday hitting a few brew pubs and eateries in Fremantle.
I spent a Sunday enjoying Kings Park and Subiaco

I was there in early June and the weather was fantastic. Not hot, not cold. Really fun.

I can't tell you whether its worth flying cross continent, but I really had a great time.