To clarify, this is about an older model surface pro, however Krahulik/Gabriel indicated that the SP3 didn't improve on the pen lag that seems to plague the entire form-factor.
I just brought it up because Krahulik is one of the louder cheerleaders of the Surface Pro line, and so one of his colleagues in the same field that disagrees is worth reading too, even if that article is now a bit dated with the launch of the SP3.
http://www.pvponline.com/news/surface-pro-vs-the-cintiq-13hd
Basically, Scott Kurtz found that the stylus lag on every tablet was so bad that he ended up using his Wacom Cintiq, which requires a wall-outlet.