We have several - DW has an expensive one and a cheap one.

We find the cheap one is made of quite thin cotton fabric, and it slips a bit through the rings - it won't stay tight. That can be a bit annoying. The more expensive one is made of thicker fabric, and it stays tight.

We love them - I have worn Lily in it for long periods - several hours, with no problems barring a slightly sore back (which was probably because I was doing a lot of bending, I was cleaning the house). She settles really well in it. I walked her to the shops and back yesterday, then prepared tonight's dinner, and cooked last night's dinner, and she was still asleep in it when we got her out for feeding a bathing.