Basically, he's calling game over for Intel's x86 chip architecture, which has been at the core of personal computing since the 1980s.
As he points out, the top-of-the-line iPad Pro costs $1,079. Add the $169 Smart Keyboard, and that's still about $50 cheaper than the least expensive version of the new MacBook.
Yet, in Gruber's testing, the iPad is more powerful and has a better screen. Plus, it gets better battery life, as iPads always have.
That's a big deal. The understood trade-off between tablets and PCs were that tablets would give you more portability and convenient new features like a touch screen, but you'd sacrifice computing power. At least with Apple products, that no longer seems to be true.
There are still advantages to using a Mac over an iPad, like expandability and more ports. Gruber has some specific complaints about the iPad Pro, but most of those relate to the iOS 9.1 software and how it interacts with the new keyboard. Basically, if you're trying to use the Pro like a laptop, it will frustrate you, as most other reviewers agree.
But Gruber believes that the future lies with the ARM-based processors used in the iPad and most smartphones, rather than the x86 architecture used by Macs and Windows PCs.
As he writes:
The entire x86 computer architecture is living on borrowed time. It's a dead platform walking. The future belongs to ARM, and Apple's A-series SoC's are leading the way.
He may be right, but this is an Apple-centric view of the world.
Microsoft's new Surface Pro 4 is a combination tablet-laptop - much like the iPad Pro - but because Microsoft is four generations into the concept, the keyboard generally works more like a traditional laptop. The Surface Pro also runs the full Windows 10 operating system, which means it can run PC programs. Business Insider's Matt Weinberger generally loves his, although he's noticed some performance issues and crashes.
The Surface Pro 4 runs an Intel Core processor, based on the x86 architecture. It costs about the same as the iPad Pro for a similarly configured version.
We haven't had a chance to test the iPad Pro yet, but we'll be doing a head-to-head comparison next week. After that, we'll have a better idea of whether or not Intel can compete with ARM in portable computing.