Hi there expo,
I'm a melburnian so thought i'd poke my head in to this conversation. (yes, melbourne is better than sydney, but no, melb uni is not better than monash )
Sounds like you've already decided on melbourne, and good on you for that. It's a great city, and if that is important to you then you'll have an awesome time here. I've got a quite a few melburnian friends (students/public servants) who have made the move up to canberra, and I think all but one have found the transition quite difficult. Which is not to say that that's everyone's experience - but it's not an uncommon one. (Although ANU is a great uni - so for some people that makes up for it)
Anyway, seeing as you have decided on U Melb, my only tip is that I would also steer away from campus housing if you can. I've tutored students in the past at their residence halls, and while they are nice and new, they also had (I thought) a bit of a sterile feel to them. And there are great places nearby that are only a quick tram or bike ride away - carlton, fitzroy etc. If you are interested, I would jump on Gumtree to have a look at places to rent - I think Craigslist is not really functional in melbourne (well it is, but it doesn't get much use - most people just post on gumtree instead).
Alright, well good luck with the move down here whenever that is. If you have any questions feel free to ask!
PS - yeah we did have a crazy hot spell this summer, but 48C is the exception rather than the rule! Although it was quite amusing to walk around in what looked like slow motion, and to see people (myself included) slowly melting into the pavement...