I am not sure if it is the lighting or not but the lip doesnt appear straight with top edge of photo. On second look it might be that you have too wide a margin on the left and right, or maybe top left is too dark compared to top right. Just seems unbalanced.
Good details. The colors are close enough to see the similarity, but just far enough apart to seem to clash. Also, the composition is a bit static -- maybe from being centered horizontally.
I lke the thought of this picture, but the two fdifferent shades of red makes it look like two completely diffetent colors. Maybe making the cup more clear and darkening the background couold help.