I'm quite shocked to see some of these reviews. I've had some very bad experiences with Estate Agents - Duck and Hedges are by no means the worst. I'm in a slightly different situation as the property found through D&H is managed by a very consciencious landlady so I don't have any experience of D&H as managing agents.
However, I must say that D&H went out of their way to find us a property matching our needs and processed the letting agreement in a week with very little trouble. I had no problem with their staff and all went well. In fact, they even dealt with a worried landlady who was double checking everything.
It sounds like some people have had a bad time, but some of the reviews sound a bit unfair.