Im inclined to agree with Crompsin. The pistol grips have a certain "cool" factor but they are downright unpleasant to shoot. Also, its hard to do any kind of aimed shooting - you dont want to be shooting from the hip in a real world situation.
The only time I have ever seen a serious shooter rock a pistol grip shotgun is when the shotgun was used as a breaching tool, rather than a primary weapon. If you have a moment, check out the stocks made by Knoxx. From what Ive heard, they are fantastic at reducing recoil AND cutting down on the overall length of the weapon, making it easier to handle quickly and effectively.
Knoxx Recoil Solutions