I used it to my 2 kids, so i wouldn't know what would be the difference. My kids are "alert" even at 1 month old, sleeps thru the night early, but also had a share of horrible tantrum.
I lent it to a friend who has a a very naughty son, used it for #2, she swears that it really makes a big difference. For her #3, she buys a unit as i can't lend mine as i got preggy too.
If you can, then go and buy, nothing to loose except for the expensive price of it, i think it's almost $1,800 now at bumps to babes.
I still have my unit if you want to rent it out, just for me to help you if you are keen on using it. I'm not selling it yet.