Not sure what happened to my post here.
Anyway, if car is under warranty, using anything other than VW screenwash will invalidate it. Having said that, there have been known problems with washer jets jamming due to crappy washer fluid.
I've used halfrauds - both ready mix and concentrate. I've had the same issue with both - namely smearing. One would smear when using the washer/wipers (despite new blades) and the other would form a smeared haze when the water started to dry off the screen.
Have had no issues with the VW stuff so happy to continue using.