Ah yes I remember the GAMSAT - i can't imagine having to sit through it twice. An 8 hour day, and mine was a saturday. Came out of the thing with a pretty bad headache - as you really have to keep your concentration up.
My year (2003) - the essay section was the worst. I just hate writing essays, at least the science questions there is some logic at arriving at the right answer.
Anyway, the GAMSAT experience is worse than anything med school throws up at you. Once you get in, its pretty hard not to get through. The hard step is getting in at the first place. There are big exams at the end of 2nd and 3rd year, though they are mooting the possibility of a first year barrier as well. 4th year is littered with smaller exams, more specific to the rotations you've just done. 80-90% of people get through the barriers, so yeah, GAMSAT is the hard one.
The interview is much easier than the GAMSAT, but theyve changed the format (i will be an interviewer 🙂 - six stations now) so i dont know how hard or stressful it is for people now.