Bear,
That's a difficult question, because my books aren't up-to-date and won't be till January 2007 and I've only been using a WFP for about six months.
From from my daily takings, purely from a financial point of view:
I'm averaging about a 15% to 40% increase.
But overall, I'm not earning a fantastically massive increase in my turnover.
I'm getting a bit lazy to tell the truth and have been quite happy to plod along in some of the Winter months, working a four day week and earning exactly the same as I was when I used ladders; working a five day week.
I've taken on some new work, ideal for WFP, and find I can earn the same as when I worked trad, but in much less time.
I think the biggest plus for me at the moment is a huge percentage increase in my 'quality of life'. I'd say around 50%!