I'm a big fan of the Pistol Grip and M4 style adjustable stock configuration. Works great as long as you have a crossbolt safety. I think the main advantage to it is that it moves your hand down and forward, putting your grip closer the fulcrum of the gun's balance. If you saw off some barrel, or get a shorter barrel, you can get the center of gravity almost on top of your hand.
The adjustable stock I've found useful too. I keep it all the way in for quick home defense and moving in tight quarters allowing it to be easily tucked under the arm for when I need to really tighten up, or it can be extended outward for outdoor shooting.
The downsides of the pistol grip I've found are that, since it moves your grip downward, it puts the force of recoil above your hand rather than in line with it causing more barrel rise, but a combination of training with the grip to compensate, and having a firm grasp on the weapon will eventually correct this. I've also found that if you fire in a hurry and didn't correctly brace the stock against your shoulder your right wrist is going to eat the majority of the recoil and if you're shooting buck or slugs, you'll be feeling it in the morning.
Still I think the good outweighs the bad for a pistol grip.stock combination. I wouldn't encourage pistol grip only though. There's probably very few situations you could get in where you'd need the extra mobility of having no stock as compared to just a fully collapsed adjustable stock tucked under the arm.