More useful things than Tenille, who has the wrong idea about me. But, like her, that's not important.
As for my giant post, I was being sarcastic. I wasn't bagging people out for treating their HSC as the pivot in their life - after all, it is the most important thing we'll have done to date (in terms of life changes). This time of year ALL HSC students turn it into their life anyway. Well, us selective kids do at least. It's not everything, but if you want a "high flying" career you certainly need to pretend it is. For a little bit.
For mature age entry, your UAI still matters. What they look at is your UAI and any other experiences you may have gained in the years since. If you've done jack all you're still not getting into uni. To improve your chances of entry you need to do something related to the degree program you want to enter, like a TAFE course or a related job. Laz can give more details.