Wish I could travel more! It's expensive to go too far from Australia too often - luckily there's plenty to explore here...
I add my vote for the Museum of Sydney (find out more at http://www.hht.net.au/museums/mos) about 10 years ago
Just last week stayed in a serviced apartment - Quest on Flinders Lane. Just near the funky laneways, Federation Square and Flinders St station and a whole bunch of tram stops. It was a great central place to check out the city from. It was one of the few places we could find to accommodate 4 people for a short stay (most serviced apartments you have to stay for a few days' minimum). It was very comfortable and modern, 2br, 2 bathrooms, laundry, kitchen, everything. We booked through wotif.com and got cheap rates too. Check them out at http://www.questonflinderslane.com.au/ about 10 years ago
Check out the Petronas Twin Towers - heaps of shopping in the mall underneath and you can go up to the observation deck between the two towers. Tickets to that are free, but get there early to get them. Another thing I loved last time I was there was going to the Selangor Pewter Visitor's Centre (which is between KL and Batu Caves). It was a fascinating look at the country's history, with a tour of the factory and a step by step look at the process of making pewter products. You can also join the 'School of Hard Knocks' and make your own pewter bowl using traditional methods. It might sound odd, but it was a really great experience and I highly recommend it. (website is here: http://visitorcentre.royalselangor.com/vc/) about 10 years ago