I imagine it brightens the rig to a pretty decent degree in the front if you don't have a full roof rack installed.... less light if installed. Of course in hot/sunny climates this is more direct sun and "greenhouse" effect. For the money so far I've configured without it for the above reason, and for added insulation against heat loss in the winter, and maybe slightly less rode noise, especially if you have the roof rack. I appreciate that it's not electric as such things are just one more expensive thing to break. I've had a Volkswagen with a sun roof (2005) which eventually had drainage issues, causing water to leak into the cabin creating huge problems... necessitating the whole interior to be removed to get rid of the mildew. The drains get full and it overflowed into the interior. I'd bet this IG design would have that in mind, but just something to think about. The problem in the VW didn't occur for about 10-15 years, but it was a massive ordeal when it happened and not something you notice or diagnose until your interior panels are discolored. The IG drain design is probably much more robust.... I just had an experience which made me think twice about if it's worth the sun roof or not. I imagine being able to stand up on the seat and look outside while 4-wheeling or something... the fun imagination... but if that ever happened once or twice, still probably not worth it for the money, especially if financed... plus the slight additional road noise, summer heat, and winter heat loss... I dunno.