A physical keyboard is a must for any tablet if you write a lot of emails or create documents. I tried Microsoft's Touch Cover. The textured pressure-sensitive surface of this cover looks and feels kind of fuzzy. After a few days of practice I was able to touch type on the Touch Cover. However, I'm a lot faster and make fewer mistakes typing on, for instance, the Logitech Ultrathin Keyboard Cover for the iPad.
In addition to QWERTY keys, the Touch Cover offers a small but useful touchpad with left and right mouse buttons. Like Apple's Smartcover for iPad, the Touch Cover provides a magnetic on-off function. This means that the display turns on when the cover is opened and off when it is closed over the screen. Another nice feature of the cover is that the keys are disabled when the cover is folded behind the Surface, putting it into tablet-only mode.