I was fairly certain that I wanted to do a Biomed double degree at Monash from about year 8; here's why:
Why Monash? Aside from the fact that it's a prestigious, highly-regarded university, there was also the communal factor. I'm Jewish, and Monash has had a strong historical (and current) connection to the Jewish community in Melbourne. Many of my friends' parents earned their professional qualifications from Monash, and I grew up hearing good things about Monash from pretty early on. One week into uni, and I have to say that I'm not disappointed; though it is a whole different kind of stress that what is experienced in VCE.
Why Biomed? In short, it's because I want to help people. I'd do med, but a) I'm not really a 'good-bedside-manner' sort of person, and that whole pseudo-professional interaction aspect didn't really call to me and b) Because I love biological sciences and, as above, I want to use that passion to help people in the future. Biomed is a pathway into medical research and biomedical technological development, and these two very broad areas are frontiers in science that are so worthwhile.
For example, the father of a guy I went to school with is currently developing the bionic eye (albeit at UoM *shakes fist* - here's a Google Talk that he gave:
http://www.youtube.com/watch?v=jOokLf3frwE)
Why a double degree? I love biological sciences, but I need to do other things as well

. I didn't really want to do arts or anything like that (because I can't face writing another essay so soon after VCE), so the B.Sc I'm doing alongside Biomed gives me scientific breadth.