Ian, Lounges are only 1 aspect, I would also consider the benefits of the miles/points/avios – ‘free flights’ which come as a benefit.
Consideration must be given to ones travel pattern.
My travel pattern is Asia, N America and Europe and all I can confirm is that over the past 3 years when I have been travelling to Europe, especially Frankfurt, Dusseldorf, Milan and Dublin, thanks to One World, I rarely need to pay anything other than avios payment which at the moment is something like £35 for a flight.
This year alone I have made 20 sectors in Europe using Avios and when I pay for a flight to Asia, in net terms, the airline is paying me to fly with them.
One World certainly works for me in 2015…
I will confirm with excitement, that I am certainly looking forward to trying out the new Bangkok CX lounge in a couple of months.