Yeah - I used to feel like Arment was in he bag for Apple (and I say this as a hardcore Mac guy, though I use Android phones), but these days I find myself respecting his take a lot more. Gruber...no. He is a very good writer who uses that skill effectively, but he's so far in the bag it's not even funny.
I think Arment has realized he really has nothing to lose, and everything to gain by just speaking the truth. A number of times he's been hosed by Apple sitting on an patch release for overcast, he's not invited to any events, and doesn't get embargoed gear. As a result, telling the truth improves his braaannnd (read that with a zombie like braiiiinnsss sound), with very little downside.
I wouldn't be surprised if we'll continue to see more honesty from Arment - I think he's realized that it only did Siracusa good. Gruber, who I love his reading, is in a tough position - he has to tow the company line in order to get the invites and gear from Apple, which are somewhat important to DF.