For me it's less about how the game played- I don't care if there's more A-spec races but having played GT3 and GT4 and hated them, GT5 and before that, GT5P, are the ones that make me appreciate the series. Sure, I would love a more realistic tire physics but to me the FFB is already quite good (as I've quoted before, Stefano Casillo of netKAR and Assetto Corsa shared the same sentiment) and to me it's the driving experience that makes GT5 what it is.
What I would like to do is suggest to Kazunori Yamauchi that he should hire Stefano Casillo (once Assetto Corsa is finished around Xmas 2012) even if it's for consultant. Circa 2003, Stefano lived in Tokyo although I know he doesn't speak Japanese but he admires the GT series (and Japanese women) and I'm sure Kazunori appreciates a bit of Italianate in the next GT. I shall tweet Yamauchi-san (using my Polyphonie Twitter Account) and make the suggestion.