Well, as for Arch Linux, that might be possible but the boot loader, as you mentioned, "IS" fixed because the tablet has no BIOS in any sense.
Apple, in their case, recompiled their programs with little or no changes because Apple modelled the PowerPC after UNIX (Xerox's system, actually).
There is a version of Linux that is piecemeal at the moment that 'might' run on it but however, if you do manage to bypass the Secure Boot and be able to boot it for installation, that is a one way process and no going back - to include installing a different
version of Linux. Since the machine has no BIOS, there is no method to identify a USB device for bootup. Currently, that is managed with the Windows Boot Manager.
Asus did the same thing with the T100 Transformer. The Windows Boot Manager was fixed and could not be changed. Several people, including myself, tried to get Linux to boot up in it. None would work, but good thing! No drivers for the touchscreen and
WiFi are available.
Currently, the RT based machines "could" run some .NET applications if written in a generic fashion and with instructions compatible with a RISC based processor. It would not be a program worth anything but it would prove that it could work.
The one thing that is locked on these tablets is the firewall. Everything relies on access to the firewall setting to include games and sticking with Windows RT - you won't get anywhere there.
I would say to wait about 6 months to a year and there may be a version of Linux that will run on it. It is in the works but was designed for the single board computers coming out. Some of those will be using the Tegra series CPU and the code should work.
Some Linux distributions can already work around Secure Boot now.
As for anybody running any regular Windows software - they can forget it. Even if you manage a VM setup to run the Intel instruction set, you would run out of space (an emulator).
Bottom line, it is not worth the effort, at least not yet.