Very simple hover script. Use in conjunction with WASD controller handling planar movement.

Hover.cs

using UnityEngine;


public class Hover : MonoBehaviour
{
	public float maxDistance, maxForce;

	private Vector3 forceVector;


	void FixedUpdate () 
	{
		RaycastHit hit;

		if (Physics.Raycast (transform.position, -Vector3.up, hit)) 
		{
			if (hit.distance < maxDistance)
			{
				forceVector = Vector3.up * ((maxDistance - hit.distance) / maxDistance) * maxForce;

				rigidbody.AddForce (forceVector);
			}
		}
	}


	void OnGUI ()
	{
		GUILayout.Label (forceVector.ToString ());
	}	
}