I got so fed up with Visio that within an hour or so I was able to discover that I should be using OG and that it could import Visio XML files and save them back. However I am left with a couple of questions:

1) Can OG import Visio stencils - or perhaps the question is whether Visio can export them in XML?

2) I exported my diagram (it has fibre raceway components on it) and after some OG edits, sent it back to Visio to add some more stencil items. I found that on re-import to OG some components with curves were starting to look quite distorted. Are there known issues with this process?