I used one from about 5 months from a few months- we never had any accidents and Inever left her in it for an extended period of time. It was a good way of keeping her distracted whilst I put the dinner on etc.

If I remember rightly there was a little toe walking afterwards. She still walked from 10 months though and hasn't looked back - no problems at all.

It's great as a device for a short period of time.