I find Med Science @ UNSW to be interesting (I enjoy looking at dead bodies in anatomy lab classes.)
But there are some people who mistake medical science for medicine (some, but very few, 2nd year BMedSci students @ UNSW are able to transfer into MBBS @ UNSW with advanced standing)
I'm sure there are some people who look down (and throw taunts) on bmedsci people like me (for "failing" to be a med student.)... but so far, I've only encountered one person on boredofstudies so far (not in real life yet).
As for your 2nd question, I'm trying to get into medicine as soon as possible (I don't really care much about completing my B Med Sci, I wouldn't mind if I have to stay back in med sci for another year or 2, since I have med sci friends who are in the same situation as me). I will sit GAMSAT next year (if I screw up umat and interview this year, though I think it's very unlikely I'd get in interview this year).
I've heard that GAMSAT is very hard, but at least the competition is not as tense as for the UMAT. (but if you do a science degree @ any uni, you'll be goin' good for section 3 of the gamsat paper). From some statistics that I read some years ago (maybe from one of the official ACER pdf files), the med/biomed science students had one of the highest successful rates (I can't remember if successful for just GAMSAT, or if successful for getting an offer into MBBS).... but that rate was between 25-30% (which is not very high for "highest").... maybe I should try to find some newer statistics to see if rate rate has changed much.
If it does make you feel at ease, @ sydney uni, you only need a 65% average in ur bachelor's degree (credit average) to be considered, and it's a threshold, so it does not matter if you get distinction or high distinction...you only need credit. The good news: many (but not all) unis in Australia use the credit-average threshold. Iif you pass the threshold, ur uni results no longer get looked at, and ur chances of getting into medicine would then depend on GAMSAT and interview.