I must say it has to be the worst experience i have ever had. 100% of the time i found my self frozen or racing myself because no one else can move. i know see why xbl has every reason and right to charge a monthly fee.
I played it the first week it was out. I haven't gone back to it since I got X-Men Legends 2. The first week I played seemed fine to me except for the fact that I could only find a max of 6 available games at one time if I was lucky. And every game you join it takes forever for the room to fill up. I can't ing stand seeing people enter a room only to drop literally 5 seconds later. I have no idea why people do this but I hate them for it regardless. And then they're people who actually wait until the game has started and then drop after the first race in a circuit or as soon as they get taken out in road rage. However, these problems are the fault of people who play the game and not the game itself.
XML2, on the other, probably has the worst online implementation ever. BO3 is a godsend compared to it.