Very nice pictures. Timing and composition is great.
I' love to shoot ballroom dancing too, it is more misses than getting most of the shots right. Your write-up is very enlightening for any photographers that do in-door action photography. Do you mind to show a picture of your gears.
For sure taking video of ballroom dancing is a lot easier, I end up taking videos instead of still pictures. You can see my videos here: http://youtu.be/SWsKWYc5B_A
Thanks for sharing your technique and experience.