I had the same issue after I upgraded to DK28 and then used Odin to go back to stock 2.1.
But since I've upgraded to 2.2 -- the lag was still present -- I used to phone's Horizontal Calibration tool... and now the screen orientation is fast and responsive.
Menu>Settings>Display>Horizontal calibration
Give that a whirl before using the described method above, which will also fix things nicely.
Horizontal calibration tool did nothing for me had to run sensorcalibutil_yamaha.