Cockpit view might be good for replays... but i don't think you can run the fastest using it. Personnaly i've been using the bonnet installed camera view since it has been introduced in GT4. I need to know where the wheels of the car are if i want to achieve a fast time, just like in real life...
The sad thing is (in my opinion) that we could have a lot more premium cars (if not all premium) if PD didn't have to go so deeply in modeling the cars interiors. I'm not saying that modeling the interior so perfectly is a bad idea, but i'd rather have more than 600 cars looking premium from the outside than having 200 perfectly modeled interiors especially in cars that i would never drive...