He is famous entirely for writing fawningly about Apple products, which appeals to people who need others' validation to justify their purchases.
he took the idea from dean allen, who had created "textile" (which was featured in the movabletype blogging-system gruber used).
gruber reworked that idea slightly, then released it with a catchy name, and somehow received all the credit.
as for gruber's blog, i would say it is evenhanded and informative, albeit focused on apple and its products. the blog is certainly not "fawning", and i think most apple-buyers feel no need to "justify" their purchases.
Evenhanded and informative? https://news.ycombinator.com/item?id=9345962
Any time Apple has a product in a space where there are other competitors, Apple's products are magically always the best in Gruber's blog.
I'll avoid offering my own impressions except to say he reminded me of the Lockergnome guy.