Strangely enough, I feel like this would be more impressive if it rendered more slowly. Does anybody else remember waiting several minutes for a fractal to render? These days, it's so easy to forget how amazing it really is.
Depends on the fractal. I occasionally make HD animations (using Ultra Fractal), and those run about 1 hour PER FRAME. A short clip takes several months, just to render. (search for jockc on youtube if interested)
You might enjoy this JavaScript turtle graphics renderer I built. It has a few sample fractals and everything renders incrementally. http://obadger.com/turtle/