I got them a couple of weeks ago and I really like them-they enable you to really flex the boot forward without it being sloppy. I bought the Expert/Race version-one down from the top model with three straps. I run it under the shell and against the tounge as the instructions say to.
Installation was easy-I just unbolted the old strap, used a soldering iron to make holes in the booster and refastened it.One mistake I made-I miscalculated where the elastic would end up when tightened and had to change the location of the mounting holes.
I think they have helped my race times slightly-sorry I didn't get them sooner. My boots are Atomic CS 140 from a couple of years ago.