I found the results quite accurate as it placed Type 5 as my strongest and Type 2 as a runner up. This is consistent with my having taken an introductory workshop which is the more traditional way of determining ones Enneagram Type.
Using a computer metaphor, Psychological Type might be considered the hard wiring of the psyche, archetypes are the software that come with the package that can be activated at the appropriate time, while the Enneagram is like software that has picked up a virus. It is based mainly on the defence mechanisms we have learned to use to cope with our environment. (New thinking on the Enneagram also suggests that we are born with our Enneagram Type.)
In the latest APT Bulletin (Vol. 24, No. 3 - Summer 2001) Pat Wyman has an article on the usefulness of knowing both the MBTI® instrument and the Enneagram scores of a client. (She has an upcoming book called Three Keys to Self-Understanding that will examine this relationship.)
The Enneagram is even more nebulous than Jung/Myers theory when it comes to finding out your true Enneagram Type. So an Enneagram instrument has to be considered as only one factor when determining your type. Nevertheless, it is worthwhile taking the test and then doing some reading to see if it has you pegged.
The booklet also contains short descriptions of each of the 9 Enneagram Types.