Yes this is a modern Windows PC using the WinRT runtime on ARM. It does not run legacy apps, but it provides Office, mail, people, IE10 and a variety of other applications. It even has the desktop with the usual Windows applications such as Paint, accessibility and Mary Jo Foley even got her beloved notepad. More importantly, it has a real file system that integrates with my home and business networks and lets me summon files from my network or the cloud.
For most people, it is a Windows PC. As for development, I'm thinking of porting my authoring system to WinRT, the only thing slowing me down is deciding how I convert my UI to the new one, as the development environment is the same old Visual Studio and when I compile it, I can compile it for the Intel Pro version as well. That will then allow me to develop HTML.Javascript applications on the Surface - will that make it a "computer" in your rather strange definition?
This is not a cut down Windows, it's the new Windows and as developers port their legacy applications to the new environment you'll see they perform even faster.
Oh and when my Surface updates (which it did without any problems, it tells me not shut down my PC, not my consumption device