A big thing is technique. Not just aiming the movement the right way, also making the movement precisely in a way that isn't jarring. Don't kick the floor in jive!
Maybe technique is important (well, "maybe" probably isn't the right word), but I seem to remember reading a news story a few years ago about a troupe of professional dancers getting ready to put on a show at some theater and they found the stage to be incredibly hard. They refused to even rehearse the show until something was done to soften, or loosen the stage surface, which the theater owners did. If a group of professional dancers won't dance on a solid floor, and we can assume they knew something about technique, then why would amateur dancers do it? Of course, how many amateur (beginning) dancers even know to stay away from solid floors?
The way I look at it, a dance studio has two products to offer their clientele. First, their teachers and expertise. And second, their floor. I wonder how many studios have sacrificed having the best floor they could afford by spending money on things like custom paint jobs, cool artwork and mirrored disco balls. I'd rather take lessons in a warm or cool warehouse with a top-notch floor, than go to a studio that looks like the Roseland Ballroom, but has a thin, wood-veneer over a concrete floor. All the niceties can come later.
I'm looking at building my own studio behind my house somewhere in the future and you can rest assured that the floor will be one of the most expensive items in the building.