Despite the high cost (when compared to 'comparable' x86_64 hardware) I am very excited by this.

However I'm concerned by desktop Linux support and graphics driver support. It would be really miserable to get this kind of machine and then have a lacklustre desktop experience (though I'd be using it as a high-horsepower workstation, it would need to be able to dump computations onto the GPU and use ordinary free productivity software on the side).