Really, its all relative. We all have different aptitude abilities. Some guys say the test is easy, some say it's tough. I found it tough because I wasn't prepared. I forgot how to multiply fractions, divide decimals, etc. However, by far the most difficult part for me was the spatial ability section. Seeing the timer going and trying to fold those dang boxes was challenging. There is a book by one of those tutor companies (princeton, or barron, or something) and its called the Mechanical aptitude and spatial ability study guide (something like that). It has a lot of strategies on how to do well on the test. For example, it can tell you how to approach the question, where to start folding the boxes, some tricks the testers use, etc.
I know some guys say its an inate ability and while I do agree somewhat I must say there is a lot you can do to improve your score. It's like IQ. We are all born with a certain range where our IQ will end up. Its the environment that we grow up in (school, proper nutrition, stimulating activities) that determines "where" in that range we will end up. So for the test, even though you may never get 100%, study so that you can get the best score you are capable of.
Hope all that made sense without getting into a discussion of Weschler, the WAIS-R and IQ testing!