we spent a couple of weeks in adelaide last year and thoroughly enjoyed it; we stayed in west beach and spetn most of our time with relis who live in elizabeth and klemzig.
we found lots of free stuff to do, driving was pleasant (although many may contradict that opinion) and the stuff we did have to pay to do was cheap by uk standards. of course we were in holiday mode so the budget wasnt an issue so we were spending uk money rather than aussie earned dollars - i appreciate that when you live there, paying to do things may be more expensive :)
we also felt safer than we do here in the uk ... but there is crime and the weeks we were there, a murder occured in adelaide that was reported as gang related, and we encountered a couple of hoons doing donuts nearby one weekend! (it was a tad amusing cos everyone came out onto the street to see what was going on ... 2am ish so you can picture the scene)
I suppose there are drug problems, and the crime that comes with it, but compared to where we live now it was pretty peaceful .
A reccie trip is a must, but if you cant afford it then all you can do is research on the net and use forums like this one to find out what you need to know.
cant help with the visa question im afraid cos we havent decided which one we are going for ... hoping to be moving over to adelaide around june 09, depending on family stuff
forgot to say, when we came last year we had our kids with us, age 9 and 6 and had no problems keeping them amused both on the flights and in aus