I like the copletely black background, the ultrasharp image with only the needle slighly out of focus to indicated motion. Catching the needle on the side of the metronome placed the body of the machine in the right side of the photo. The arm provides a straight line and strengthens the photos. Very good job!
I like the sense of movement, maybe even a longer shutter speed to get the arm swinging across the whole face of the metronome would have added even more interest. The lighting is farily bland and it could have been cropped more tightly to reduce some of the background which doesn't add anything to the image.
I wish to hell this were squared up vertically and horizontally; it only wants a smidgeon of rotation to accomplish. the motion is very very nice, as is the framing. Was the pure black groudn your best choice?