Tried it once waaayyy back years ago, sometime during the reign of Rameses 11, and it was disgusting stuff. Come on, how difficult is it to boil up and few spuds and mash 'em ?
I also hated those little Smash men from space. Everybody loved them, except moi!
I use Asda SmartPrice Instant Mashed Potato. I ignore the microwave instructions on the side of the packet and simply put what looks like the right amount for one person into a bowl with a very large knob of butter. (OK, it's actually Willow, not butter). Then I add boiling water until I've achieved the right consistency. It's the butter/Willow that makes all the difference; it's just as good as doing it the hard way and actually cheaper!
Does anyone eat smash any more? Well, millions of French folk find its the very best way to make the famous 'voile' potatoe ie very runny mash. They buy loads of smash and pricier brands. So next time you buy an expensive french meal with pommes de terre voile, you'll be enjoying smash. And most of those delectable pommes frites are oven chips.
I buy a 2Kg bag of spuds from my local Asian supermarket for 69p yes that is not a typo. I boil them and mash them with a ricer and add milk and butter. Once it has cooled I put individual portions in re-useable microwaveable containers and just heat them up as needed.