I am using the Rouge grid now. Its pretty good with disciplined subjects that can sit or stand in place during the set up like when I have my wife as a subject. However with the kids who can't sit still, since the light source is so small, their little movements make a big difference in the effect. So for that I am looking into different larger modifiers, like maybe a Qbox 16 or 24 or a photoflex strip box with grid.
My grid system just came with one free sample gel. Most of the time, I am using the grid as a hair light or background separation light to control light spill back to the camera and adding flair. When I want to gel the background I use the Rouge gels that attach to the bare speedlite, but I haven't really played much with gelling the background through the grid. That mostly because one sample I got was a pink color and well its pink... I would like to lick up the set of gels for the grid at some point in the future though.