The Saxon PC grids are lightweight, easy to use and take up minimal space in your camera bag. The main potential hassle with them is if you upgrade to a better flash, your current grid may not fit on the new flash unit.
The grid for the camera's pop-up flash is a bit on the tricky side. It's taped in place with a reusable tacky plastic, that provides a less than secure grip. Using this device with your camera's pop-up flash will be challenging at best.