I like watching players who show lots of emotions. Of course, sometimes it can distract you from your play but also sometimes it get enlight the fire inside you that is needed to win a match that you normally wouldn't win if you continued playing uninspired shit.
Always depends on the player if it's good or bad and on the situation also I would say.
I love it when Hewitt shouts his C'MON or Nadal his VAMOS or when Kiefer's energy level is VERY high or when Waske is cheering up Haas in doubles or if Safin smashes a racket
That's part of the sport and this makes it especially interesting for me to follow certain players..... otherwise go and watch a 10 hour chess match
it's also sports at a very high level, but maybe a bit more quiet