Overall it looks good. My comments are mostly minor.
line 203: 'access' appears twice.
line 256: You have an issue about whether values should be subjective
or objective, and then you leave cost as subjective. I would suggest
that "low", "medium" and "high" are of no use in most circumstances.
Since practically no one looks for "high" cost products, every commercial
print shop will have only "low" cost devices, no matter what they charge.
"low" and "high" are in the eyes of the beholder, i.e. client.
If we don't want to have cost and an integerUnits value, then I suggest
we delete it.
line 273: the 'ppm', etc. values should be preceded by some words that
tell the reader that they are units of speed and they should be spelled
out so people don't have to guess what cps means.
line 277: there was a suggestion to replace device-id with an info url.
Perhaps this should be added as an issue.
line 294: We got rid of marker type from the model because we felt it was
detail that most people didn't care about. Perhaps it should not be
in the directory either.
line 311: Shouldn't there be a media attribute too so people can search
for B size or transparencies. As with other attributes, this would
show the values typically supported rather than values of media that
are ready.
line 311: The document does not address whether there is or is not an
extension mechanism for adding additional attributes to a name
service entry.