I purchased a set of the CDs and used them when I studied for my test. Lots of very useful information that will start anyone serious about tree care down the right path. The ISA is an international body, so testing applies to everyone.
My set has been passed around quite a few times, but I always end up getting it back. We've started a book sharing club, of sorts, between the arborists in the area and that seems to be a very good way of getting to know each other and to share a cup of coffee once in a while as we meet to test new gear, or talk shop.
Joel