I wear one and have had deer very close with the right wind.. inside ten yards without a clue that I was there.
On public land I have also had other hunters inside of ten yards, usually just passing thru.
Not ideal, but it happens on public ground.
One guy stopped to sit down five yards in front of my brush blind to take a break and eat a snickers candy bar.
He was very surprised I was there, to say the least, when i spoke up and reminded him not to litter.
I have two, an ASAT camo suit and an Ameristep leafy poncho and sit on a small chair, inside or behind brush blinds made of existing foliage.
I carry the suit in my backpack and put it on when I get to the blind.
It helps to build blinds ahead of time. I build blinds out of existing brush in the off season and mark their location with GPS, so I can walk straight to them in the dark.