Well, to answer the question, no I haven't actually - whereas at high school you would do homework, assignments and what not, and all you'd really need to do to learn the actual course content is show up and be taught (and the teacher would spend time helping you if you weren't getting it), at university, staying up to date is a very real challenge - there is no such thing as "oh well the class is not up to it yet we'll take another day or two on this" - the lectures WILL occur as planned, and the rate at which new knowledge is taught would throw high school right out the window - I recall the physics lectures in mechanics that covered roughly two weeks of year 12 or 13 physics in each 50-minute lecture (although it's mostly not that intense.)
What I'm saying is that as GG said, you're literally flying through the course content (and having to do much work to keep up) right up until the week before exams, which means it's very important to be revising as you go, and even if you only take a day or two to consolidate the entire courses in your mind, you'll still only have a few days before the first exam, so it is, in my opinion, impractical to use many past papers then (and during the semester you can't use them to their full potential because there are questions you simply won't be able to answer), so really past papers aren't hugely practical. Just as well the exams focus on breadth of knowledge rather than depth of understanding - you won't need to read over the question styles and the marking schedule for the key phrases to include in your discussion, in fact, there's not much to discuss at all. Other than the HUBS mini-essays, I'd say the way to earn marks in SAQ would be to give concise, succinct (on-target) answers, no waffling like NCEA (or worse, schol - you literally only have to waffle about something remotely related to get some marks there), so you're far better off knowing exactly what you're talking about by learning stuff from your notes, rather than trying to find out how to answer questions to get the mark like in NCEA.
EDIT: It's not as stressful as it sounds, as long as you keep on top of everything. Also, wow I'm slow - the discussion has entirely moved on while I typed this post up...