I do Engg/Comm at USYD. Engg is a 4 year degree while comm is a 3 year degree, so that should give you the approximate ratio of engg/comm subjects you'd take over the course of your degree. You're able to combine any engineering major with commerce, so Aero is fine.
As sida said, whether the degree is good or bad depends on what you like. But if you do enjoy it, then job prospects are good as it opens up both engineering and commerce jobs (and there are also a couple of grad positions in engineering companies where they have specifically wanted a combined engg/comm degree). Some people view doing a 5 year degree as a downside as it's more time "wasted" in uni and less time in the workforce, but you've got another 40+ years of being in the workforce so I don't really agree with that (and uni is fun time as well). Feel free to ask anymore specific questions if you've got any.