Does anyone have any pics of their rifle set up like this? It would be bonus if they have a seekins sp3r that's what I think I want but I want a longer hand gaurd.
Some fools rest their barrels on barricades and such while shooting. This greatly changed point of impact. A longer handguard protects against doing that. Also it looks cool. What else do you need?
Advantages -- It lets you grab the rifle farther forward while shooting (for greater control on rapid target shifts), gives you longer sight radius for the irons, gives you more room to attach accessories just where you want them, and like wormydog said, gives you something to rest the rifle on without changing your POI very much.
Disadvantages -- it generally requires getting rid of the factory pinned on front sight, which is sturdier any of the rail attached ones. It requires attaching the front sight to the rail, which floats independently of the barreled action/rear sight, and if you put pressure on the handguard, it can shift your POA (only really an issue if you shoot slung up with irons).