I received my culotte slip very punctually, and wore it yesterday for the first time. For women who want to know real information about fit, this is a full review. Others can move on. :)
I was a little apprehensive about sizing because I'm very pear-shaped and so often wear one or more sizes smaller on top than on bottom, and all the pettipants I've had before were rather slim in the thighs. This one is great! I'm actually 25 weeks pregnant and it fits well over my belly and I never had any bunching or binding in the thighs. The length is great, too--I'm 5'7" and it sits a little above my natural waist because of pregnancy, but still reaches a couple inches past my knees when sitting. The legs don't ride up at all (an issue I've had with looser culotte slips) and I was very comfortable all day. I would say I couldn't feel the slip at all, but I was aware of it in a good way--I could always comfortably feel that it was where it belonged. It was wonderful to be able to wear one less layer over my belly. The fabric is not as soft a nylon as Flo-Ann slips, but I think this actually helps it "slip" better, and it isn't scratchy at all. The inseams are placed a little back, too, so they don't rub against one another. I anticipate that this will mean a longer life!
To give an idea of sizing, I ordered a 2x. My pregnant "waist" (about 3 inches above my natural waist) is 36" and my hips are 52". I currently wear an XL in most brands for skirts and leggings, so I sized up one for pregnancy. If you're slim-hipped you might want to size down, but I think I would use my regular size if not pregnant.
The only thing I don't like is the snip-it part. I wish the company would make this in different lengths instead, because the rows of lace are a little rough and caught on my knees a bit when sitting. I want the full length, so cutting them off won't help. But that is a slight discomfort, well compensated by the practicality of the slip and being cooler in the summer heat...