Continuity

If it weren't for the little stain on the mirror I would have thought that there are really a lot of cups on that bar <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" title=" (Smile)"/>
So, the angle from which the shot was taken is great. I consider the wall on the left a plus, as it suggests that the shot is authentic and unplanned.

Regarding the composition, I like the simple subject of the image and the few details you provided. The minimalism of the image lets the viewer focus only on the presented image without disruptive elements.
I also like that the cups are visible only in the mirror as this lets the illusion of infinity linger more in reality <img src="e.deviantart.net/emoticons/b/b…" width="15" height="15" alt="" title=" (Big Grin)"/>

The light in the image is good too as it accentuates the idea of infinity suggested by the 2 mirrors. And it also adds something warm and pleasant to the whole atmosphere of the image.

As a whole, you demonstrated a wonderful concept, a good technique and quite an original shot. Keep up! <img src="e.deviantart.net/emoticons/b/b…" width="15" height="15" alt="" title=" (Big Grin)"/>