I tried it on Sunday. The setup leaves a lot to be desired. You have to sign up for each attempt, and they're only recording the fastest laps. However, since it's a one-lap race, the people that are (randomly) seeded at the back of the grid get an advantage, since they cross the line at a greater speed. You can sit at the start for 30 seconds to try to avoid the traffic, but the average player is so bad that you'll probably still run into them. I did at a wet Suzuka, and of course they ran me off.
There's also no accounting for people running dirty laps. Oh yeah, I was told it'd be the same track every day when I was there on Media Day, but it seems its cycling out daily. The car stays the same though (M3 GTS).
That said, I made it to the top six. I just checked the stream (Feb 18), and they never did update to my fastest time (a 2:37.1). Honestly, it's run really poorly, but there are some genuinely fast Forza people out there!