An anti-plaque mouthwash is not meant to remove plaque - rather, with regular use, prevents it from building up as quickly. So most people might find it difficult to say if it works, or not.
I use an anti-plaque toothpaste every other day (with Braun electric toothbrush) and have not needed my teeth descaled at the dentists for years.
I had a small filling done today(if you consider £72 small) and I took the opportunity to ask my dentist for his view.
He said that he does not rate them as much more than breath fresheners and that he does not use one.
I think that I shall stop when mine finish.