A couple of quick points on storing/transporting a gun in the glove box:
1. In just about any vehicle, it takes at least a few seconds to reach across the car, pop open the glove box, access the pistol, acquire a proper firing grip, and actually bring it into action. If you find yourself in a situation in which your attacker has a hold of you and is trying to drag you out the drivers side door, or you are perhaps using your left arm to try to keep an attacker at bay, you can pretty much forget about reaching over and accessing that pistol. Worse yet is if your attacker actually enters through your passenger door before you can stop him, he is now in a better position to take control of your gun than you are.
Now I know you're thinking, "I ALWAYS have my doors locked". Well, I would say that even the most religious door locker screws up every now and then. In addition, a car jacker may walk up and smash your window in with a tire iron before you have time to react anyway. And in the worse case scenario, the car jacker will come up with the gun already pointed at your head. Do you think you'd be able to access that gun in the glove box in time to save your bacon in such a scenario?
2. The glove box is typically where we keep our insurance cards and our vehicle registration. Having the gun in there with those papers only serves to complicate traffic stops.
IMO, the gun should be immediately accessible to you when you are in the vehicle, and it should also be accessible to you if for some reason you are drug out of the vehicle. A gun in your car won't do you much good when you are lying in the street getting the stuffing kicked out of you by some thug. If you have it on your person in some kind of a holster, it's likely to stay with you in that situation.