By all means, come to Australia! But Sydney? Really? Don't get me wrong, Sydney's fine, I suppose, if you happen to like stupid traffic and idiotically high density living. Sydney and Melbourne are both too big for my liking, but they are where all the trendy people live (at least, those who like everyone to know that they're trendy).
I grew up in Canberra. It's a lovely town (only about 300,000 people last time I checked) and 80 or 90% of the state is national parkland. You get more of a feel of the Aussie flora and fauna just driving between suburbs than you ever will in the bigger cities. It does get cold (but it's only a couple of hours' drive to the ski slopes in winter if that's your thing) but the houses are built for it. However, as Doomsie accurately pointed out, it's as boring as bat-shit. A great place to raise a family though. I could go on because I know it better than other cities, but I'll stop myself here. Oh, and without wanting to hurt anyone's sensibilities... God gets his drinking water from Canberra.
Having never been to Adelaide, Hobart or Darwin I can't comment on those cities beyond the commonly held opinions that most Aussies have of those places... Darwin is just too hot and humid, don't try breathing there unless you have gills. Adelaide is pretty, but inanely dull. Hobart (and indeed all of Tasmania) is gorgeous, but cold, and somewhat isolated.
Perth is the capital of Western Australia - a huge state that occupies the western third of the country and contains mostly desert. I have relatives over there, so I've had occasion to visit a couple of times. If I could choose where I wanted to live in Oz, Perth comes a close second (Canberra still wins, even though the weather depresses me, because it's my home). It is a very neat (tidy) city and the people are much friendlier than they are in Canberra - as a general rule. The downside is that it is just so far away from everything! Mind you, that could be a good thing.
And then we come to Brisbane... about an hour's drive away from Surfer's Paradise (aka the Gold Coast) and where I currently reside. For me it's a nice blend of big city facilities and small town space. It has a reasonably good public transport system and the weather is divine, however, we are in the midst of a drought at the moment which translates into domestic water restrictions. Having said that, I have never come close to hitting the limit, and it really is quite easy to be just that little bit more environmentally friendly. There's a fantastic indie scene here (not to be confused with Indy, which is on the Gold Coast) and the girls take MUCH better care of themselves than they do in cities further south (where they're rugged up for a goodly portion of the year). Seriously, it's a tropical oasis with indoor plumbing. The humidity knocks me around a little bit in summer, but it's tolerable.
Oh, and I think the Aussie dollar is currently trading at about US$0.60 which is good for you.
Anyway, that's probably more info than you wanted... I'm just trying to get my post count up without anyone noticing.