Hi Andrew,
Welcome to the forum.
As long as the job is in the same IT skill then it shouldn't affect your visa application. They are looking for the fact that you've been in the same skill and so have experience.
Location depends on your IT skills (and whether you can work from home
),
but Sydney and Melbourne are probably the biggest IT places. If you check out
JobServe Homepage that may give you a better idea.
I don't follow the IT much any more since I'm winding down my IT work in favour of my online business from home.
Regards,
Karen