Not sure if this is something which can be helped in TE2011, but maybe it's something to consider for future versions:
When playing on grass courts (especially if the grass is pretty bright), I'm having some difficulties with following the ball trajectory. Yellow on bright green isn't all that clear to make out, and it's straining on the eyes.
Maybe the game could have an option of changing the ball colour (into red for instance, for increased contrast with the green grass)?