i was worried when i took mine out that she'd notice it being more "open" than she was used to (not sure if you know what a snugglenest looks like, but it has sides to it from about the torso area up to the head, as well as a "headboard" at the top, if that makes any sense. it's open from torso down, but the positioners are at the torso area), and that she wouldn't feel as safe, but we just went with it, and if she noticed, i didn't notice! if she does, it's just like any other transition, and you can maybe slowly wean her from it if you think she needs that (mine had a little mattress pad that the positioners were attached to, and my plan was to keep her on that for an extra day or two if we needed to). good luck!
julie