Dance Til We're High is a well-written story. It starts with Twilight Sparkle wanting to have a date, wanting to have someone in her life - a special someone, more than a friend. She speaks with her friends, and ends up going to a costume ball, where perhaps true love awaits... At a single chapter in length, the story is a reasonable read, and the characters mostly feel "right".
The central premise of the story - what drives the conflict - is that Rainbow Dash was the one in the mask who danced with Twilight at the ball, eventually forcing the pegasus to confess her admiration and love to Twilight. This scene is fairly well-done and reasonably believable, and is a decent use of a somewhat-used plot device. Twilight's varied reactions are in-character - at first anger, then confusion, and finally acceptance, and in the end, her getting together with Dash - or at least trying a relationship - felt right, which is exactly what needs to happen in a shipfic.
Overall rating: B+.