Anyone have experience with analog Hall Sensors?

[RayStoner]

I'd second N8's comments.

I know that they have hall sensors that have sufficient resolution to use as encoders on servos. Your application seems similar to this, ie, you want to detect the rotation of a magnetic field and use that measured angle to make a determination of what piece it in proximity to the detector.

Some things to consider.

Hall sensors measure field strength
Field strength is going to vary with distance.
Rotation of the magnet is seen as a varying field strength and also a change in polarity
Field strength changes due to distance and rotation are essentially indistinguishable

If you can control for the factors that affect field strengths, you should be able to accomplish what you would like to do.