I think that this would be great for HFT, but ... what do I know.
They’re crazy because they are so unstable that you basically can’t reboot them and expect them to reliably come back up, so you are stuck on that given kernel version and firmware etc (important for eg the custom network cards that often want firmware updates).
You just turn it on, run it for like a year, and then it dies and you trash it and get a new one delivered.
But I'd agree on the bleeding edge being generally more bleeding than edge (esp. from a performance engineer perspective) with problems ranging from kernel not supporting TSC calibration correctly to acpi issues to faulty (fried) instruction cache.