I have not really compared the fork sag before and after. One of my reasons for the upgrade was to help maintain some more cornering clearance when pushing the bike a little in the twisties. I also upgraded my rear suspension with an Arnott air ride system. Between the 2 , I definitely have accomplished that goal.
As far as rough roads, I do believe the forks handle this stuff better and the front wheel feels more firmly planted across such stuff. Keeping your tire on the road, of course, is very important for traction. I will also comment that it seems the front end has got even better after some miles ridden on it with the new Progressive Monotubes. Almost like there is a little break in period.