I stayed at that Marriott - easy walking distance to everything. Right next to Chinatown if you dig it.

For a quick trip I would recommend hitting up the farmers market. You could easily get lost and spend all day but it's worth it just to be a part of the madness and to pick up a few cheap souvenirs from local artists, etc.

If you plan to splurge on a nice dinner I would highly recommend Tjanabi - it's in Federation Square but don't let that deter you as being too touristy. It's a super nice place with all the "australian" food you can eat - emu, kangaroo, wallaby, crocodile, bay bugs, etc.

I recommend roo and emu as they were my two favorite proteins I found while there. A bit pricy - but not really when you look at the US/AU conversion rate. When we went we had an excellent wine from Summerhill Wines in AU - and the very vitner joined us for dinner!