A MagMod starter kit will set you back about $90, which is reasonable, considering everything you get: 1 grip, 1 grid, set of 8 gels.
No, I don't use the MagMod. I've used the
Rogue Grid for several years and have been happy with it. The Rogue has been out awhile longer, so if I was shopping for something like this today, I'd probably go with the MagMod because it's a sexy looking rig.
For what I shoot, I only ever use the Rogue as a hair light in my studio, and it's great for that purpose. I've used it for dramatic spotlighting also. I have other traditional modifiers that I use with my speedlights (umbrellas, softboxes, etc) that see a lot more use.
The MagMod (or Rogue) would be great for someone just getting started, or who doesn't want/need a lot of off-camera options. I've kind of moved past that.