About the pros - I've been watching this for years with very little understandng of the finer points
Originally it was all traditional ballroom and latin. I remember when Brendan came along, and he was much more mobile, he'd move with the music, relax a lot more, the choreography was much more varied and interesting. Then all the eastern European dancers arrived with again more varied and non-traditional moves.
Now the younger contingent (Kevin and Janette for example) have relaxed it even more. You can still see the traditional steps, but the choreography, the music, the costumes are all much more contemporary and cross the genres a bit, so the traditional bit of the dances seems to be mostly in the steps - the rest is much more variable, if that makes sense.
Of course the addition of the Charleston, and the fact that there are some quick dances in every show (jive, quickstep, etc) has made it much more interesting for those of us who know very little about the right way to dance. We just like the "show".