I'm hoping that it would react sooner if just one tyre lost pressure.
Nice to have, in case we run over something, but does not replace the walk around the car before each journey.
Due to the wife's commute over the field of broken glass via the boulevard of rusty screws (seriously no idea how she gets so many punctures) ours has been tested extensively.
It's detected punctures before the tyre looked obviously soft but you don't know when they actually occurred so god knows what the actual response time was.