I use space saver bags all the time. I usually put towels in them and then use them for all my dirty laundry. They do save space, but for some weird reason, I think they make your suitcase really heavy. It might be all the stuff you can compress then you think you have extra room so you add more in your suitcase

I have used them for the kids clothes , and if you are careful in packing I don't see any more wrinkles than normal. I don't leave the clothes in for an extended time. Good luck!
Just saw the posts before me---my bags were from QVC and don't require a vaccum. They work just fine. You put your things in and then I lay them on the floor and squish out all the air(this usually involves me looking really odd, laying on my bag, using all my weight to push the air out--but it works). You can then roll the bag like a sleeping bag to get the rest of the air out.