But Surface (and more so the second versions announced) isn't just marketed nor targeted at being a tablet. It makes a great laptop when you have the keyboard/cover. And the new docking station solidifies its place on your desktop.
I use a Surface Pro for development - even running Hyper-V with a couple of VMs at a time for testing - and am quite happy with it. The screen could be bigger, but that doesn't make for a good tablet and the docking station will help fill that void (not to mention multi-screen development is easier in various scenarios anyway).
And while I probably don't need a 512GB SSD (256GB should be plenty since I use cloud storage for a lot of stuff, much of which isn't cached locally), the 8GB option at $1300 is comparable to - and even better than some - laptops/ultrabooks that are reasonable for development.