I own both a Surface RT and an i7 touchscreen Ultrabook, and I will also be getting a Surface Pro.
I use the RT for everything around the house. So if I'm watching TV and need to make a quote, or look up something, or need a recipe while in the kitchen, I use the RT. It's the perfect form factor for quick and easy access wherever you are. The keyboard and kickstand make a MASSIVE difference, and are awesome. I also love that the keyboard cover has a mouse trackpad.
Then my Ultrabook I use for coding at home. I don't have a desktop in my house, so when I am away from the office I use the ultrabook. Really the only thing that my ultrabook does that my RT doesn't is [in my use-case] run Visual Studio.
Finally, I will be getting a Surface pro to half replace the Ultrabook (to code occasionally), but also to use as a note taking device. OneNote is really a stunning piece of software, which I use to record pretty much everything. Personally, I would pay a bit more for a Surface RT with a pen, but I guess I will just get the Pro.
Basically: Surface RT does MUCH more than just consume media, Ultrabook is nice and fast for work, Surface Pro is a nice inbetween.
To address the lack of 3g: I actually would never buy a 3G model because why must I have 2 seperate sim cards? The simcard I have in my phone has data on it (obviously for my phone) and calls, so why must I keep another simcard topped up in the surface? In my case, my Windows Phone has tethering so just turn that on and connect the Surface.
@DrJohnZoidberg, Essentially you were excited for the sake of being excited. The hardware didn't change, the software has only got better.