yes, the stink....be warned!
I've used it off and on for years and find it does make a difference - small but detectable - I'd be really surprised if a company fleet manager was wasting money on such stuff though...
Personally I swear by 120 ml of acetone to a full tank of diesel. Mind your paintwork as neat its excellent paint stripper apparently....but it definitely makes the engine run more smoothly and responsively....again its not a mega leap in performance but noticeable - makes the engine quieter too...my previous motor had it for the best part of 100,000 miles....zero problems.