Not really Rog, It depends on the detergent you use to a degree.
Also a factor the first time you use WFP on a property that has been cleaned with trad methods for donkey's years, is the fact that there can be a residue build up over the years on the edges of the window panes, the pure water gets into these little cracks and disolves a little of the residue, sometimes it can take a couple of cleans to get rid of it.
But if you decide to squeegee the windows one month, by the time you go over them with your WFP the following month, there simply hasn't been enough time for any residue to build up, hence there is no real problem
As for a stiff neck, I think it is just something you adapt to, or perhaps you are standing to close to the building?
I will also change hands frequently as I am working, haven't had any probs with a stiff neck or other muscles myself though.
Regards,
Ian