The problem with the DRS (well I think, anyway) - comes in three parts.
Firstly, it is being used as a tactic by the batting and bowlng teams - it was never intended to be used as a tactic, it is designed to lessen the number of incorrect on-field decisions.
Secondly, you can't have an international-standard competition where one cricket board can actually CHOOSE not to use the system whenever it sees fit.
Finally, the creators of the video technology have stated that LBW reviews through hawkeye follow a "predicted" path and that therefore the accuracy is not 100%. I just cannot cop that a ball can be shown flicking the outside of the top corner of the leg bail, and because it is doing so by two inches either side of the stump, a decision can be reached either way.