The Dalrymple thing doesn't surprise me--once Gruber left, he filled that role of communicating with ardent Apple fans.
As for Tumblr, Marco was also a co-founder! I think he has much more to say about businesses than Gruber, who often analyzes businesses by comparing them to Apple.
Or Jim Dalrymple, who in my opinion, took the on the role of official Apple apologist for the 5by5 Network when Gruber left.
He also has much more to say on entrepreneurship (given his first-hand experience with the App Store).
He was also the lead developer behind Tumblr during its rise, which I imagine involved some entrepreneurial thinking.