Magic Tracer is hands down the best raster-to-vector conversion program I've used so far. Good feature set, easy to learn interface, and good price point. These are some of the main things that make this program so good.

ELgorithms MagicTracer is quite easy to use. I found it to be a powerful program that contains both raster and vector editing features. The user interface is nice because it gives real-time previews for any adjustments I may do before I apply it. Also the vector results are excellent. The performance to price ratio is also excellent. Highly recommended.