I never drive with cockpit view anyways so I could care less about standard vs premium. GT5 has done a fantastic job with making each car "feel" like it should, ie the Veyron feels like a lead sled the Mugen like it's riding on rails. So that makes getting standard cars a great experience.
So what if I can't add wheels and a I can't use it in photo travel? Who gives a 🤬? This game is supposed to be the ultimate driving simulator, not the ultimate replay / picture whore beauty contest simulator.
Not to mention, there are standard cars and then there are what I consider to be standard+ cars. Most cars fall into the standard+ category (like the Veyron). They are clearly ports, but work has been done to clean them up a bit and make them respectable. That leaves the standard of the standard. Cars like the Beetle RSI that appear to be PSP ports or something because they truly look horrendous. However, in my experience these PSP ports are the minority of "standard" cars.
My standard RS6 has a few rough spots, but overall, in an online race or whatever, you wouldn't be able to tell if it was standard or premium.