I have a number of concerns about the WP article on Cardinal Vowels, some of which I have already mentioned.
1. I think it's essential to make it clear that the system works through training in its use, something which is not mentioned in the article.
2. Although the CV diagram in the Cardinal Vowels article looks to me like the real thing, the vowel diagrams on all the dependent articles on specific vowels reproduce the Wikipedia version which has a lot of extra vowels added. In what I will call the WP-CV diagram you get this (note that WP labels this "IPA vowel chart"):
3. The distinction between Primary and Secondary Cardinal Vowels is a very old one. I have never read a proper justification for the use of this distinction. Why are Primary vowels primary? Is it (as I suspect) because they are thought to be easier to learn and produce by speakers of European languages, while Secondary vowels are the hard ones for us? I think that in the context of the languages of the world it is wrong to imply that in some way Primary vowels are "unmarked" and Secondary "marked".
The next step in sorting out WP's treatment of CV's is to consider the recorded examples. Leaving aside the controversial Mid and Central vowels for now, it sounds to me as if some of these recordings need to be improved. [ɛ] has a lot of noise in the recording. [a] is not fully front and [ɑ ] is not fully back. [ɔ] is too close. [œ] is a poor-quality recording. The [Œ] vowel, admittedly a rare and difficult beast, sounds nowhere near what I would expect - it is not rounded enough, open enough or front enough. [ʌ] is not back enough. Finally, [ɨ] sounds rounded to me.