Dan,

> If the portCount and portName primitives used by this 
> facility work on all platforms, then there is at least the 
> promise of things being pretty civilized.

Yes, but remember you are asking for *MIDI* ports not serial ones.
Here's what you get on my machine:

MidiPrimTester new getPortList '
MIDI Ports:
	0: Microsoft MIDI-Mapper (out)
	1: Microsoft GS Wavetable SW Synth (out)
'

Both of them are MIDI ports - neither of them is a serial one.

Cheers,
  - Andreas