The security features could be very useful for the big internet companies, Amazon, Google, Facebook, etc and they can afford to spend a few tens of millions of dollars on something speculative like this. And they do, with things like Arm or OpenPower servers.
There's also the high end embedded land where you don't need to run a traditional operating system. Network switches, cell towers, that sort of thing.
For instance are there big problems out there that are compute intensive, but branch-heavy enough that GPUs aren't a great fit, in applications that need low power but that don't make sense as "cloud services"? I don't know.
The optimist in me sees potential opportunity in opening up new domains. The practicalist agrees with you; it's going to be an uphill battle and a lot of stars need to align just right. But if they really can deliver 10x on general purpose computing workloads, it's hard for me to see that not being game changing.
And I'm still looking at recompiling, debugging and deploying a ton of software to see advantages from the Mill.
So whatever advantages it brings, they need to be very substantial (i.e. if the next-gen of Intel x86 chips still out-perform it, I'll buy them) and quite quick - because I can go 5 years not buying the Mill while Intel promises to support me for their awesome new architecture. I mean, probably we buy some Mill machines, but how likely is it that it's game changing on my codebase?
That's where I see the problem. There's this whole huge assumption that the Mill will yield a bunch of benefits. If they're clear cut (a huge if) then they still have to beat their competitors being able to brute-force performance improvements until they come up with a new architecture themselves, which can take advantage of the very compensation they're asking from their customers ("switch architectures, it'll be great we promise").