IMO, for all people who say it's boring, maybe you guys are looking at arcade type racing ala Initial D or Wangan Midnight?
I'm 10 hours in the game almost non stop. (posting now because I'm hungry and made an instant noodle) And I feel it barely started. You have to take your time and start working on unlocking everything, then you would get the full GT experience.
One suggestion for all people playing is... DO NOT TRY THE DAMAGE. I was fooling around with it and I got a 190K RAPEIR (yes I meant RAPE) bill.