The wagtail is a really good piece of equipment, and for me it is the squeegee and applicator of choice.
Looks cheap, is certainly expensive for what it is, but it is a bloody god tool once you get the hang of using it.
The cloth applicator part is certainly thin and doesn't hold a lot of water, but you would be really surprised just how far it will go, and it is just so light to use.
You have to work at the technique though, and it is fantastic on insides. Though I have found that I need to do a little more detailing than I would otherwise do so with a separate applicator and squeegee.
As I am mostly WFP I don't use it above ground floor, but do use it on plenty of shop fronts where WFP isn't the best choice.
Had mine a few months now and the washer part is also still going strong, cheap enough to replace anyway.
Ian