My Personal View - They are lovely to watch. Gentle slow stately rotating wings, a bit like a surreal flying swan on a stick!
There were a few of them on Water Board land a couple of miles from where I used to live. On a quiet day it was a nice place to visit and watch their gyrations. I don't recall hearing much other than the wind that had always whistled over that spot.

As for efficiency, I have never properly researched the lifetime energy budget for them, but have always had a feeling that taking them from unsmelted metal ore, through manufacture, transport, erecting and routine maintenance it would need to put a lot of energy back into the system before it finally wears out, for the balance to end in an overall energy gain.
That said, total energy produced is not the only factor. Daily running does not produce acid rain or particulate pollution (Don't know about the manufacturing processes). Also, if energy is produced by converting wind power, it may reduce the need for some proportion of fossil fuels currently being burned.

In my book, the main thing I would like to know is an accurate assessment of the energy produced versus consumed and whether the result is a gain or a loss.

If there is even a small overall gain, I would like to see as many turbines as could be built. Put them down the central reservation of every motorway in the UK at a height above the lorries. Stick one in my back yard. Give us forests of the blades on desolate hillsides.

Build Jerusalem among these white angelic mills!

That said, I think that water power, tidal and water wheels should not be ignored. Water powered the Industrial Revolution in England.
Quack!
Geoff the Duck.