I agree mostly with guga, except that I honestly enjoy Marat's tennis. When it's on, it is absolutely a thing of beauty. And of course, there is the "you never know what you're going to get" feature with Marat, which makes each match an adventure.
Of the list, probably the only person I don't enjoy watching at all is Berdych.
Everyone else has at least something in their game that I enjoy. I'm especially warming to Gonzalez.
You like Safin's game and not Berdych's? That makes absolutely no sense to me.
P.S. If the reason is the Madrid incident, it does make sense to me, but that's not connected to Berdych's tennis.