There are already a bunch of DLC cars available online, considering the relatively tiny ammount of cars in the game (or atleast it seems tiny after playin GT5 prior to this) i find it quite insulting that they are selling cars. Heard they are planning to release all the exclusive preorder cars in 3 months as DLC, to milk some more money out of the game.
I really don't like companies that do this kind of thing with their games.. don't release half a game and then sell the other half off in spare parts, its not like TDU2 is jam packed with cars and content, if you focus on simply racing the Solar Crown series you will run out of races pretty quickly, most car classes only have a few cars available to race in them, until you get to A2 and A1.
/rant
I've grown quite fond of my Veyron Super Sport, there arent many of them around, but the standard Veyron car is way over used, they are popping up everywhere as it is by far the most popular car, i've also seen a lot of the DLC (different colour) Veyrons around.
Zonda Cinque is the only other competitive car in the game, which leads to the problem of only seeing the Cinque and the Veyron being used for racing, and in straight line speed nothing compares to the Veyron.
Favourite cars for me though.
Mclaren Mp4-12c
Ferrari 458
Ferrari 308
Ferrari 612
Lancia Delta
Caterham