In my experience most ARES groups at least who use HF are familiar with NVIS principles.
Many groups don't use HF extensively, but here in Oregon we have a regular state-wide net
and use HF to link the various counties with the State EOM over distances of 300 miles.
In fact, one of the problems we sometimes encounter is from people who try to be too
strictly in accordance with the military NVIS approaches, in spite of the fact that (1) they
were initially based on flawed computer modeling using a poor ground model, and
(2) most ham applications aren't worried about the enemy DFing our positions.
Even some of the ham "conventional wisdom" can sometimes lead folks astray. For
example, over the last 3 sunspot cycles we've had relatively little coverage around
Oregon on 40m, even at mid-day, so we've needed to use 80m during the day and
160m at night. I've given a couple presentations and distributed antenna designs
to get on 160m because often that's the only band we can use.
The Australian Ionospheric Prediction Service has a handy "Local Area Mobile Prediction"
tool online that shows expected coverage vs. frequency and time of day for distances
out to 600 miles:http://www.ips.gov.au/HF_Systems/7/1
Also, some of the "serious" NVIS operators make too much of a deal about keeping
the antenna low to the ground - a few feet. This does make it harder for the enemy
to DF your station, but it also reduces your signal strength unnecessarily. Higher
antennas (when possible) reduce the trip hazards and are often easy enough to
accomplish in practice. A good maximum
height in feet is the band in meters,
which is easy to remember. So not higher than 40 feet on 40m (which is rarely a
problem for most hams, unless their primary interest is DX). Lower is OK, but
especially on 160m you can lose efficiency as you get below about 20' or so.
(The original computer models used a MiniNEC ground equations, which greatly
understated the losses at low heights, making it appear that an antenna 3' off the
ground gave significant gain.) You can still use those very low antennas, of course -
I put one up at the local hospital that was laying on low bushes beside the parking
lot - but there is no penalty for getting it up 10' to 20' in the air when you can.
I build a couple sets of wire dipoles for 40 / 80 / 160m for the ARES portable trailer,
and we use them on Field Day as well so folks get experience setting them up. While
both of those sets use loading coils to shorten the 160m elements, in practice I've
never had a problem finding space to run full length wires for a portable exercise
(including, in one case, across the County parking lot, wrapped around a small tree
and tied off to a stop sign in front of the County Commissioners' building.)
But the important thing is getting out and doing it. Using NVIS requires some extra
skills and knowledge, such as choosing the right band. I've done workshops where
we practice tossing a rope over a branch and setting up a 28' mast with just one
person (which are equally applicable to improving your VHF/UHF antenna system.)
Getting out and setting up a station a few times a year allows operators to get the
feel of the band conditions throughout the day, for example, and the sort of signal
strengths they are likely to encounter. And this was in a county where we could
talk to the State EOM on simplex with a line-of-sight path, so HF wasn't something
we were likely to need in many situations. But there were still some corners of the
county back in the hills where it could be useful.
So, yes, I expect many hams are using NVIS antennas. The bigger problem is perhaps
to get them to think of using it for emergency communications, and to prepare for
those situations where VHF/UHF aren't sufficient to the task.