So after two months some feedback.
I've tried the XP-Pen 03 on Windows, and it worked absolutely fine apart from a bug with Capture One where one could have either pressure sensitivity or the second mouse button. Could not recheck with the latest C1 build, but PhaseOne did open a bug for this, so it hopefully is fixed by now. LightRoom worked just fine with it.
One the Mac it worked just fine everywhere I tried, including C1.
After two weeks I shipped it onwards to my sister who has been using it happily since it arrived (she uses Macs and the whole Adobe zoo). She often uses drawing paper on top and traces her pen sketches with the tablet.
For my own use it is definitely too big. The bit of retouching I do is easily done on the small Bamboo. So I did not order one for myself.
cheers
afx