I have a set of Tanita scales. In terms of accuracy, they are reasonably stable from one week to the next: I use them every Saturday morning and get a very consistent answer: I've been at 17.0% for each of the last 6 weeks (according to the scales). I've monitored my fat over time using them and seen the fall from 22%. As to whether I'm actually at 17 though, I'm not sure, I reckon I'm closer to 12%...
However, I would question the basis of calculation. You have to enter your gender, height and whether you are child or adult. It then weighs you, before calculating your fat. I wondered if it was using this data to estimate what it thought I should be in relation to norms, so to test it I put a ruck sack on my back full of books. Hey presto, I'd put on 15Kg, but guess what, apparently it was mostly fat (I think it was showing me as having gone up from 17% to around 24%). Maybe it's the type of books I read...