Servo savers are a mixed bag from what I have seen, TC6/6.1 comes with a nitro style saver, everything else I think does without.
Problem with them, is many turn your steering to mush, but that is subjective, I know some won't run with anything but solid, some glue up even the tightest designs.
Me, I was using the Top/Kim job, but actually hated how it felt once I got faster, then removed it, loved that, but then jumped some teeth in the servo.
As of my EX I got a Tamiya high torque saver, which I think is very simular to the Xray one, and so far I like it.