I don't wear heels except on special occasions, so my feet aren't use to this kind of pressure. The pain on the balls of my feet was still there, but not as much as if there wasn't. I tried one shoe with it on and other without. It is a big difference by the end of the day.
The gel pad is about 2mm thick, so for me with chunky feet, it made the shoe a bit smaller in the front - pushing my feet out of the shoe opening a bit.
They are easily removable and you can put them in another pair of shoe, which is economically great :)
As a person who does not own a car and walks everywhere these are a lifesaver for a day when I want to wear something a bit prettier than sneakers. You stick them on the inside of your shoes and just start walking (can't get much easier). The cushions literally cushion the pressure caused from tired feet hitting the pavement and I definitely noticed a huge difference in the amount of time it takes for me to get to that limping home slowly stage - in fact in a full day I never got to that stage. This is why these gel cushions are highly recommended and great for anyone and everyone. I used them in heels but I'm sure they are a great addition to any pair of shoes - even comfortable ones, if you're planning to do a lot of walking.
Tips: They tend to take up a little bit of space in the shoe (not a lot). But choose the shoe you use accordingly.