Just to add my +1 to supporting OpenType CFF fonts (based on PostScript) - most of my collection is in that format - it's not something that I want to give up.

Right, this is on the roadmap for Prince 7.0.

The first beta for Prince 7.0 is now available and it does indeed support OpenType fonts with PostScript/CFF outlines.

And Prince latest builds now support subsetting for CFF fonts!