It's not a fool proof system by any means though with Mercedes utilising their system for around 3 years now, also Caterham share rear end technology with Red Bull purchasing their gearbox and rear suspension from the Championship winners. So why do some have more success than others using the system? If we were back in the days of unlimited testing I'm quite sure the teams would have it nailed by now but with limited track time and the effects difficult to model on conventional suspension design systems the teams have had to invest time and money in the tools required to model it.
So now you know what the teams are doing I'm guessing you want to know how, well it's an area that is difficult to explain in it's entirety with images due to the teams hiding it and most of the system being enclosed under bodywork. But in a rare shot of the rear end of the Mercedes W02 we can see how the team are hydraulically linking both sides of the suspension.
In the image above found by @F1Talks – www.f1talks.pl and courtesy of www.suttonimages.com from the Korean GP in 2011, we can see a damper connected to the bottom of the Pull Rod which takes care of 'Roll' and/or 'Heave' (Heave is the up or down motion of the car) we can also see 2 Hydraulic pipes are connected to the damper and lead to a central valve block. A hydraulic pipe is connected to either the high or low pressure chamber of the damper which leads to the central valve block where it's counterpart or opposite from the other side of the suspension meets with the valve block too. This connection allows a displacement of hydraulic fluid on one side of the suspension to have a counter displacement on the opposite side of the car helping to level it.
In Malaysia we saw Red Bull and Mercedes soften their suspensions and run with less tyre pressures than in Australia having perhaps witnessed Lotus adopting this style. Meanwhile Lotus and moreover Raikkonen went a little backwards suffering perhaps with the aerodynamic changes made to his car whilst still running an aggressively soft car. (Raikkonen suffered with snap oversteer throughout the race)
Below are a few images caught of the Mercedes W04 caught during build up
Merc FRIC in action? Pitch control by dm_5167cd137b13d