Rockstar recently gave hands-on previews to several gaming sites such as Kotaku, IGN, GameSpot, and CVG. We have summed up Kotaku's preview below.

1. Cars mentioned in the preview: Mazda RX8'60s,  Ford Mustang Boss 302, and a Aston-Martin V8 Vantage Roadster.
2. You can spend money that you earn on real world name brand aftermarket parts that range from electronics to nitrous tanks. You can change your paintjob or even change your interior. Some other things that you can customize: headlights, doors, and steering wheel. There is most likely more you can customize that the article doesn't mention.
3. You now have "Special Moves" that you can change via your garage. What are some of the special moves? Rockstar exlpains some:
   * Zone allows you to slow down time in order to take sharp turns or weave in-and-out of traffic like a champ!
   * Agro will give your car added strength and the ability to damage opponents faster, or sometimes knock them completely out of the race.
   * Roar sends a shockwave that clears your path by pushing cars off to the side of the road.
   * EMP is an electromagnetic pulse that shuts down the engines of the cars around you, bringing them to a complete stop.
4. There are lots of recognizable landmarks. Sunset Strip, Beverly Hills, The Comedy Store, the Renaissance Hollywood Hotel, and the Santa Monica Pier chockablock to name a few. Billboards also feature real-life products such as iPods and T-Mobile Sidekicks.
5. You can start a race with someone by flashing your headlights.

In addition to hands-on previews, Rockstar released ten new screenshots of Midnight Club LA.

Source: Kotaku
Thanks to Adriaan for the heads up!