I did it last year.
I'm not interested in Geology and only did it because it's a pre-req for a 3rd year Meteorology subject but I found it reasonably interesting.
The field trip was really good. The assessments are not too bad, you do a few basic quizzes in the earlier pracs just like the first semester Earth science subject if you did that. They get a little bit harder towards the end when you have to make your own cross sections but it's not too difficult and you're able to discuss the answers with other people. There is a prac exam which is not that hard if you go to all the pracs, do a bit of memorising and listen to all the clues they give you. Basically you have to identify some rocks and minerals by doing hardness tests, shine, streak, colour etc. They give you a list of the minerals that they want you to know so...know them and you should be alright with the prac exam. There is no final exam for this subject (YaY) but there is a short essay related to the field trip and some of the lecture content due in the exam period. On the field trip you have to fill out a booklet which overall is worth something like 60 or 65% (i forget) of your grade so the field trip is important.
The downside of this subject is you basically give up most of your mid-sem break because of the field trip.