OK, this is more of a Windows 8 gripe, but it applies to the Surface as well. The Modern UI is aesthetically pleasing, but it definitely needs work. For instance, how do you close a Modern UI app? There's a way to do this, but novice users won't learn without doing a little research. Similarly, the Charms bar doesn't also appear when you scroll to the right side of the screen. (Hint: try the lower-right corner.)
Sure, tech-savvy users know these navigational tricks, but that's beside the point. Windows 8 lacks visual clues to help everyday business users master its new UI. And for enterprises, this means expensive, time-consuming retraining for employees. There's room for hope, though. The next version of Windows may very well address some of these UI shortcomings.