Well I've used them for several trips now and they've been excellent. I've tried them against pellets and they're at least as good, which considering that they are 14mm is good. They are definitely instant and I've had fish on them when other's have blanked.
I don't think they are quite as good as pellet when the water temps are low, which is probably more to do with size than anything else. At the weekend on the Warwickshire Avon and the Severn I blanked on them, getting several abortive pulls, whilst my mate Mick had 3 barbel including a double. Now this could have been due to other things such as the length of the hair or the fact that I was using a feeder, or that I was fishing a different swim. I suspect that a smaller diameter might have just tipped the scales in my favour.
I'd post a formal review, but there isn't a 'link' in the original article.
Well worth a try for barbel!