Problems I find with wfp.
1. Often leaves bee/fly spots or bird poo residue, partly because you don't see it and can be real pain to shift wfp.
2. Sometimes get runs from top of frame.
3. Upstairs sills can be hard to clean
4. Don't know how good finish is as window left wet.
5. Not all customers like it (majority would prefer trad.)
6. Still have my concerns of accelerated deterioration of wooden surfaces.
This is apart from equipment problems we experience from time to time and trying to work out which is best brush, pole etc. I have been wfp 4 years.