In my opinion, as long as they include a driver option to disable any optimizations and thus, ensure that reviewers are able to make fair comparisons between products, Nvidia's actions are perfectly justifiable.
I know that what nVidia did was cheating, but let's not forget that ATI (and any other manufacturer) have been caught cheating once or twice before.
Also, Carmack never said "nVidia is cheating", so I think that this post is a little extreme.
nVidia will certainly have to win back our trust, but I know that a lot of ATI boys out there have already labelled nVidia as the scum of the earth (but I bet that they once had nVidia cards that they were very happy with).
Long post short, let's see what nVidia can do next and let's keep an open mind (i.e. don't do something stupid like ban nVidia products and turn ATI into the next Micro$oft...)
For some this article was about Carmack blasting nVidia, and for some it was Carmack talking about the different products and the way they decide to do things. I'm just saying that a lot of ppl had already made their mind up before even reading the article.