This is n-trig "hover lag," a well known issue with n-trig in comparison to Wacom (the others are a "wobble" in the line when you draw/write slowly and a higher initial activation force).
Once you actually touch the pen to the screen and reach the required initial activation force (in other words when you're making a mark on the screen) that latency disappears. In fact Anandtech's tests showed that the n-trig implementation was slightly less laggy then the SP1/2 Wacom digitizer:
AnandTech | Microsoft Surface Pro 3 Review (near the bottom on that page).
If you have lag issues while actually writing or drawing then you're either expecting too much (all these inputs, even the super-expensive Cintiqs have some lag) or the problem is on the software end, but I can't address that without more info.