I had the same exact problem. 5 - 10 times per day I was loosing all touch input. On another thread I saw someone click the end button on their surface pen to show that the computer wasn't frozen, just that the touch input was out. Sometimes this would even happen when in sleep mode and I wouldn't be able to turn it on at all. The only thing that reset the touchscreen was a hard reset.
I took mine back and returned it for a new unit. A few hours in and no problems so far. The new one seems even snappier in general. I love this machine, so I'm hopeful it was just an issue with some internal connections in the first production run that a few of us have been unlucky enough to pick up...