I have the S2BR myself on minarelli. I think it's a major improvement on the existing Malossi / Polini varios. You should compare it to the EVO and MHR varios, not the normal 'sport/speedcontrol'.
-More durable, very resistant to wear
-Cheap
-Big size (19*15.5mm) rollers
-quite stable
-very large diameter > high top speed.