I came across showroom shine via a TV shopping channel (sorry Amazon) and admittedly was taken in by the claims and demonstrations. Fortunately this product isn't a complete con but neither is it the miracle cleaner Greased Lightning claim it to be.
Firstly, the liquid dries to a milky white coating when applied so unless you apply on a windless day and are meticulous about wiping and buffing, you'll inevitably spray this everywhere. Spray it onto the cloth instead before wiping on and remember to stand downwind of the car or else you'll ruin your hard work!
Secondly, do you really think you can effectively clean a car without washing it, especially getting into the nooks and crannies between panels and inside the front grille? As the white spray gets everywhere, if you're not careful the time you think you're saving will be spent pushing cloths into these tight spaces. If you simply rub this straight on, your car will look a mess upon close inspection which defeats the point of using it.
That said, showroom shine isn't a bad cleaner. It does cut through grime and tree sap easily, bugs vanish with a little rubbing but tar is another matter. Reviews elsewhere reckon that the maker's claims of tar and spray paint wiping off easily are only valid with a good precoat of showroom shine before the contamination lands on the paintwork. Must admit though, it makes glass sparkle and once buffed, paintwork does have a deep shine.
In hindsight, I should have realised that (as with most things in life) Showroom shine isn't a substitute for elbow grease. So yes, I'm back to washing with soap and water but will definitely rub this on afterwards as a final polish. Bummer.