I like the racing line! Helps me, a person who isn't fantastic at LFS, to learn the tracks a bit better!
I do however think it's quite a bad idea! As we're updating LFS and making it more realistic the devs are adding, the racing line is an example, unrealistic things to the game!
Yes, it's a good idea, great in fact, but you wouldn't get a line on the floor in real racing so personally, even though I like it, I think it should go!