As far as the lighting goes, first the bad:
It's not well optimized for the platform. This sounds oxymoronic, first party game and all, but there are glaring negatives. Some shadows flicker on and off, some shadows behave weirdly when the 24 hour cycle is turned on(don't know exactly what's technically different, but the static lighting does better), so it looks like pools of shadow that will trickle on track as the perspective moves. Everyone loading the game up for the first time at Brands Hatch knows this. Only the player's car will have well modelled headlamp lighting, which isn't an issue in the game, it just looks weird on replays. Finally, the edges where headlight's light dissipates and similarly the shadow's edge can have a tile like quality, the fidelity isn't there.
I'm making it sound worse than it is, the over all impact of all this "jank" is very rarely jarring. The good:
Global lighting and the way it lights up the interiors of cars has greatly improved. Everyone will remember GT5's early Splinter Cell-esque lighting in the cabin that would turn the dashboard completely black with straight edged shadows, that stuff is gone. Similarly, the way light gets into the crevices other than the cabin is great, I just noticed clearly last race the Mclaren F1's gold lined firewall reflecting back at me as I was behind it. Same with a Pike's Peak car I have, from behind the rear axle, differential and suspension are awesome to watch and it's not something that would ever be well lit in game in GT5. The paint on cars looks a million times better with the way it is now lit. I don't know if you want to file reflections under lighting, but clear coated paint on panels AND interior pieces look awesome. So, the FXX has a clear finish on the carbon fiber steering wheel and that's captured perfectly. Same thing with most badges that are on modern steering wheels, that finish looks great.
To answer the question, I think night racing is fine. It's actually a huge improvement from GT5 in terms of the night sky and how actually fucking dark a road can be when it's not lit up by street lamps or whatever. It may seem like a dick move to cut visibility like that, but it's something race drivers have to deal with, much like with reduced visibility in certain cars, spray from rain, dust from a dirt surface etc...
