I just recieved my Glorious XL Heavy, the edges are not super flat yet due to it being new. Coming from a QcK+ i can feel a clear difference between the two, but this difference is mainly due to a sum of attributes, it's not like the Glorious blows the QcK+ out of the water in every department, but you can say it's one notch higher in every criteria.
The glide is smoother on the Glorious, and slightly faster. The difference isn't blatant but the surface is more flat, there is no denying it. Also, it's nicer to the touch when you put your arm on it. The QcK+ felt more rough. The glide is not that much faster, meaning i won't have to change my in game sens.
The added thickness is definitely a plus. Playing on the Qck+, i could feel the cold hard surface beneah it. Not anymore, this thickness gives you comfort.
I can't feel a "start" friction when moving the mouse, like the QcK+, the Glorious XL Heavy allow me to be pixel accurate by making micro-corrections to my aim. I can however notice an added "stopping" friction when the mouse movement ends, it's difficult to notice and can be a plus in FPS games.
The stitched edges are nice considering the fact that i like putting my wrist on the edge of the mousepad outside of gaming.
Edit: Okay, so i played some FFA DM in CS:GO and i noticed my aim and target acquisition being much better. My playstyle is already snappy, the superior glide plus that stop friction thing made it snappier, my aim is sharper and the crosshair stops exactly at the place i want it to stop, resulting in some "What the **** ?" moments when i land a headshot i wasn't expected to land. For info, i play with a G303 at 1000 dpi, 1 sens.
I hope this mousepad will resist the trial of time, i don't see myself buying anything else to replace it.