I really love my Windvest too. I just recently did a 4000 mile tour of Europe on my Rune and found the Windvest made the trip nice and comfortable. Even on the 100mph+ German Autobarns.
For another thing, I don't like looking through a shield, esp when it's raining. We had some real downpours going thru Switzerland and the screen keep me adequately protected from the rain and the spray.
Like I said, I personally find there's no problems with strain from the wind. For me it gives a good balance between enough wind to let you know you're on a bike with enough protection not to be tiring.
As far as looks goes, well I'd rather have no screen at all, but I reckon the Windvest does a pretty good job of blending in with the Rune's lines. It certainly gets a lot of positive comments.
I guess height has a lot to do with whether a screen suits you or not - I'm 5'7'' but I have got it angled low.