Hi Malcolm,
I don't have a quick change collet for hand routing but I do have an Xtreme Xtension in my table mounted router which is essentially the same thing. I find it ideal for table operations as it is not only quick to change bits but, as the name suggests, it acts as an extension so as you get a greater flexibility with smaller bits (I.e. 1/4"). The down side is that sometimes you don't want the extra length when using bigger bits so do have to remove it.
I don't do that amount of hand held routing so whilst it would be handy to have, it wouldn't justify the cost for me. All said and done, with most routers having a collet lock these days, changing bits isn't that onerous!