Hi
I have the same problem on my SP7 (i5, 16GB, 256)
I had such high hopes for this device but now I'm really disappointed.
For years I had a laptop and a tablet and finally wanted to combine the two but now ... :(
I've found out that the jitter is considerably worse when there is power connected to the surface. Anything electrical (e.g. even a projector) will make the jitters unbearable!!
Also I live in Iran and aside from the astronomical price of the device here, there is no Microsoft support! So basically if this thing is not fixable via a software update, I'm screwed!
Has any body found a fix for this yet?