I've got the new one - the Heart2Heart.
I find it to be really good with Nao. She snuggles right in and tends to go to sleep (boob pillow). I pull her little feet out, but shes a bit long for her age and I didn't put her in it til she was six weeks old. I found you need to make sure their bottom is really deep in it. And make sure the straps are tight enough to bring them right to your chest.