I too run JR 9100 servos in my buggy. I've been using a 9100s for steering and a 9100t for the throttle (yes I know the S & T don't stand for steering and throttle). These servos have been in my Losi 8IGHT since I built it for the 2008 racing season.

During the 2009 season the steering servo began getting some play in it. Upon investigating I realized the servo saver was built way too tight from the Losi factory and it never really protected the serve as it should have. I corrected this by replacing the saver with new parts and building it myself.

Now in the 2010 racing season my steering servo has, as expected, gotten worse. It's now to the point where the steering jitters constantly, with the front wheels shaking back and forth rapidly, whenever you pick the vehicle up off the ground. I decided to replace it with a second 9100t rather than going with another 9100s. The T has plenty of speed and a stronger gearing so hopefully it'll hold up better.

I don't blame the JR servo in this case as my servo saver was not set properly from the factory and it took me an entire year to realize it. My existing 9100t throttle servo has been flawless and still has zero play.