Also, perfect timing to read this article, after just purchasing a Kindle Paperwhite and having it for a few weeks now.
As a casual reader, I find the Kindle Paperwhite as the perfect medium for my reading needs. I can hold it in one hand, I can read it any time of the day with adjustable brightness, and the e-ink is very clear and the font is fine. With respect to the article, I don't think the typical person cares much for typography, as long as it can be read and understood. The justification notion, I would argue that the typical user may not notice it as much as the hardcore reader. This is where I disagree with the parent post here, as in Amazon may understand "the customer" in this particular case, or at least the majority. Everyone who I've come across absolutely loves, and heavily uses, their Kindle(s). Some people even collect them! All reviews love them and it's a great experience.
The point of the article: Now, I'm all for making the Kindle the best reading device ever by adding all these cool features (justification, typography, different modes for different things like iBooks, etc.), but instead of targeting the Kindle as being deficient for most users, the article is targeting Amazon more so for it's lack of pushing the product to all it can be and I think this can be extracted toward larger companies doing what they can to push the envelope with their product. This is where I agree with the parent post, Amazon seems to be lacking in this area. The blogpost written and the parent post both point to deficiencies in how Amazon looks to their customers and pushes their products to the best they can be.