You cannot simply install any old Windows program onto the ARM version of Windows 8 (W8 RT) - the Win 8 RT platform (RT being the ARM based version of Win
is locked down in a fashion that compares to the Apple devices.
You cannot simply buy Photoshop and install it on the W8 ARM version, even if it did work. You're stuck with the Windows store model, though I'm sure it won't take users long to figure out how to sideload apps.
W8 RT also does not support many of the Windows enterprise offerings, like Active Directory. It'll be a complete bust in regards to the professional market, and the x86 W8 tablets will have terrible (in comparison to other tablets like the ipad) battery life just like the current W7 ones do.
I tried a friends Samsung tablet today, which he's running W8 on. It shipped initially with Win 7, and putting W8 on it made the experience better for usability, but the thing is still a complete pig weight and battery power wise.
Keep your eyes open, it's rumored MS is debuting a W8 RT tablet or two at their press event on Monday.