I upgraded it to windows 8.1 last night (not RT, the normal windows) I had a few issues, an intel video driver caused the screen to be upside down, but a bit of reading and I had that cleared up.
So the answer to your question is that it runs normal windows.
Its best not to think of this as a tablet, just a 10 inch all in one pc with a touch screen. It IS a tablet though, it is just a lot more powerful, and is actually "usable" in an every day environment.
I just got back from a month overseas and I used the tablet exclusively to game, cruz the web, edit photos (high end stuff with Adobe photoshop and lightroom) The machine is truly capable.
Ive got the add on dock with it, so I have 4 USB 3 ports and an HDMI port. I have it connected to my 24" asus ProArt sRGB monitor for photo editing along with a keyboard, mouse and Intuos pro tablet. It hums along damn near as well as my Alienware m17x r3 laptop does.
Definitively agreed on that. On tablets is usually the biggest issue, that they have own OS and own applications and unless you are happy with the preinstalled/provided apps, then you are out of luck.
Tablet that is basically a custom PC build is quite another story. I dubt that it is even right to call it tablet… maybe netbook with touchscreen will be more appropriate?