Great result and awesome tutorial!
The only thing I thought was wrong was that the tree shadow on the ground seemed to have a different direction than car shadows....then I saw that it was a part of the background photo! Shows how little I know about light and photography

My Photos and CGI work:
http://www.flickr.com/photos/larsmagnusson/
Software: ZBrush4, MaxwellRender2.5 64bit, trueSpace7.61, PhotoshopCS4ext 64bit
Hardware: Core i7 980X, AsusP6T Deluxe V2, GeForce GTX 480, 24Gb DDR3 1600MHz
OS: Win7 Ultimate 64bit