hi nwhilk,
Yes, i took both the MCAT and GAMSAT and i personally found the GAMSAT a lot easier. It's more a test of your abilty to take information and apply it, whereas the MCAT is more of a "how much information can you cram into your head and remeber from college" type test.
the gamsat will explain a general concept, then give you a problem where you have to apply that concept. obviously it helps a lot if you can remember the material, although some problems have nothing to do with medicine/science (i remember one debating the artistic value of a urinal!!).
I'd say these differing styles probably reflect the teaching styles at Australian vs. US schools (from what i've read anyway..please correct me someone if i'm wrong). Once you ge the pracitice test you'll know what i mean.
Hope this helps