The skill set definitely has to be there ... with that said - some of the most skillful motorcycle racers in the world won't touch that course, and for good reason. So ... balls are apparently the game-changer for the folks who choose to ride the TT. It probably sounds pretty clearcut the way I explain it, and in reality - it's anything but clearcut. Just take a listen to any TT riders when asked why they decide to ride the TT... then listen to MotoGP & WorldSBK riders who explain why they don't, and you'll hear a particularly subtle difference.
Closer to the Edge was a great glimpse at the sport, and some of the most talented TT riders to grace the roads on the IOM today.
I'd love to visit the IOM TT one day!