For what it's worth, I decided to take the plunge and buy a Heilyser oxalic
acid vaporizer (model 700).  I'm currently a hobbyist with only several
hives (Carniolans & Russians), and aspirations to go semi-commercial next
year.  I'm in central Vermont, and to the best of my knowledge, no one else
in Vermont is using oxalic acid on any scale.  The best data on oxalic acid
I've found thus far is some Danish testing:

http://www.agrsci.dk/plb/cjb/oxal-djf.htm

This data deals mostly with spray and trickle systems, but should give a
decent picture of vaporization results/effects.  There seems to be minimal
stress to the hive, and no particular evidence of mortality.  According to
the manufacturer, this type of system is becoming common in parts of Europe
and Canada.  He states that the vaporized system delivers a much more
precise amount than any of the other delivery systems.  He also mentions
that the oxalic acid (predictably) does not affect capped varroa, but can be
used as close as 7 day intervals, and can be used down to 33 degrees F.  At
$59 U.S., it sounds like it's worth a try.

Todd Fillmore
Shrewsbury, Vermont