Since we're all talking based on pretty much no knowledge about the thing, allow me to speculate:
There is no reason it won't work with a full sized keyboard and/or mouse. You already can use a keyboard/mouse with nearly any android tablet via both bluetooth and the usb port. I have plugged in a full size keyboard on my A500, used a usb mouse, and used it much like a laptop. There is an app (can't remember the name now and don't have the tablet handy) that lets you use an actual MS Word/PowerPoint/Excell, etc via cloud networking. Works and looks exactly like the computer version, and the files created pull up the same on any computer.
So, considering nearly any Android tablet already has this functionality the Surface definitely will. I'm guessing the built in keyboard will work just fine, but won't be quite as good as an actual keyboard, no surprises there. The touchpad will be a nice touch. Hopefully the price is reasonable. I'm not willing to spend ultrabook prices on a tablet, especially something unproven from Windows. If they were to do some sort of promotion like they did with the Windows Phone where people could trade in their old device for a huge discount on the Windows Phone, I would be very tempted to give the Surface a try.
I have to say, it would be REALLY nice to have a tablet with an actual OS on it. Apps are fun and handy most of the time, but there are many times where I just want to use a real program. As good as apps can get, they're not the same thing.