This brings up an interesting question in terms of historic instruments.
Here in New England, particularly, we have numerous organs from various
parts of the 19th C. Many of these have been in continuous (or almost
so) in their original churches, others have been moved from their
original locations but are still in service after rebuilding, or
restoration, or renovation. Often these instruments were built for pitch
standards not at A=440. The question, especially when moving or
rebuilding, is whether or not to retune.
 
For instance, the 1897 Hutchings in my church was built and tuned at
A=435, and over the decades there has been talk of retuning it to A=440
so that other instruments have an easier time of playing with it (this
brings up another point, since the pitch standard in Boston is now about
A=442, thanks to the BSO!). For whatever reason, retuning has not taken
place (the maintainers, Andover Organ Co., probably have a lot to do
with this, theologically :-)), even though additions and some tonal
changes have been made. One of the major reasons for not retuning has
been the _expense_: many of the pipes would have to be cut down, the
reeds essentially rebuilt, overall revoicing, etc. Andover has, over the
years pushed the tuning up a bit, so it is now set at about A=436-437;
when the weather (or the church heat) really warms up, the organ comes
up to about 438-439, so instruments have an easier time.
 
I think, aesthetically, the lower pitch level gives this instrument
(which is tonally excellent and in a good acoustic), a "warmer" sound,
even with rather prominent mixtures. The reaction of other musicians is
the same, in that they perceive it as a "warm" but clear sound,
especially when compared to other organs they know.