It's pretty good, the only problem is that it's really sharp. Especially on the tail, alloys and the wheels. It's a bit blocky too, Vectors are supposed to be smooth - do you use the Pen tool?
Pen tool will make a Vector much better and thats what I use to vector, as you can create curves to make it sleek. Problem with the Lasso tool is that you cant curve, only make blocky stroke lines. Could you post up the original image as well?
Also i'd advise if you are considering to vector a lot more than this is to download Adobe Illustrator, as that is the best Vector based program around.
Good for a first, hope it helps