Late reply because I don't visit SynthZone very often; there is little to draw me here on a regular basis.
To answer your questions I do not find the menus to be difficult, although I had to first understand the Casio way of "thinking". The menu system is actually quite logical once you understand what is really going on in the instrument. The main problem is simply that the XW-P1 has a plethora of features, so one needs to dive into the menus a lot when editing or setting things up. But....Casio also provides a PC/Mac editor for editing sounds and an iPad editor for editing the solo (monophonic) synth engine. They are free and pretty decent IMO.
Also on the plus side there is the Casio Music Forums where you will get a lot of help by fellow users (Casio does not run the site, although I believe they sponsor it).