Is it worth buying the rode videomic?

I'm currently using the Nikon d300s with the built in microphone, the video is great however the audio is not as good as I would like. I'm going to upgrade to an external mic and have considered the rode videomic, my budget is £100 so I can't afford the pro version. Does anyone know if the sound of the autofocus would still be picked up on the rode mic and if there are any other mics that are better for my budget?

Added (1). Also is it worth considering the nikon me-1?

I think it is worth

Using an external mic will make your video so much better. It will approach television quality. So long as you isolate the mic from your camera using a mount, you won't record any mechanical sound from the camera.