I have also encountered those who have "mastered" this guessing style to perfection
, but I'm still able to serve aces or their returns are easy because they are usually late to receive. I have played quite a lot of these players and I have had never any problems with them. The only one I had problems was you, since you did it in a tiebreak where it caught me by suprise. Great tactic, btw.
Anyway, what usually also helps, is to hit the really weak serve, that is very short, you know what I'm talking about, and then rush the net. That way it's very hard for them to hit a hard return.
I'm just suprised because I have never had problems with them. Very rarely I hit the serve at them, and when I do I just guess the direction of the return and usually win the point anyway.