Getting a character to fly(follow cursor in 2D) in Unity4.3

I've created a script based on the look at mouse script in the UnityWiki. I attached it to my player and when I run the script he just sits there, no reaction. Any ideas? I'm fairly noobish so it's probably something simple. Thanks! Code:

     using UnityEngine;
     using System.Collections;
 
     public class Flying : MonoBehaviour {
 
     public float speed;
 
     // Use this for initialization
     void Start () 
     {
 
     }
 
     // Update is called once per frame
     void FixedUpdate () 
     {
     if (Input.GetKeyDown(KeyCode.LeftShift))
         {   
         // Generate a plane that intersects the transform's position with an upwards normal.
         Plane playerPlane = new Plane(Vector3.up, transform.position);
 
         //Generate a ray from cursor position
         Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
 
         // Determine the point where the cursor ray intersects the plane.
         // This will be the point that the object must look towards to be looking at the mouse.
         // Raycasting to a Plane object only gives us a distance, so we'll have to take the distance,
         //   then find the point along that ray that meets that distance.  This will be the point
         //   to look at.
 
         float hitdist = 0.0f;
 
             if (playerPlane.Raycast (ray, out hitdist))
                 {
                     // Get the point along the ray that hits the calculated distance
                     Vector3 targetPoint = ray.GetPoint(hitdist);
 
                     //determine the target rotation. This is the rotation if the transform looks at the target
                     Quaternion targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
 
                     // Smoothly rotate towards the target point.
                     transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, speed * Time.time);
 
                     //Move forward
                     transform.position = transform.forward *speed *Time.deltaTime;
                 }
         }
 
 }
 }