Hi andy:
well, as i said, a little lock tight on the nuts threads would put my mind
much more at ease on one of those.
The reason why i suspect it would be less robust then a soldered connecter
is that, by the very nature of the configuration, that is, the coaxial braid
is compressed between a nut and the washer, or the body of the connecter,
the nut has some back pressure on it which makes it much more likely to come
loose then say a regular bolt and nut used in antenna construction.
There is always pressure back on the nut from the coax and if it ever got
even a little loose, there goes the ground.  Also, the nut is not being
snugged up against a solid metal peace, the soft copper of the braid is not
always solid enough to provide good enough back pressure for the nut to stay
solid against the threads.  However, with a bit of lock tight, the
possibility of it even coming loose is much reduced.
There are much more factors at work at the top of a 60 foot tower then there
are near the ground. Especially if you are rotating anything, connecters
have to be rock solid in those conditions, otherwise, climbing the tower
will become as common as changing underwear.
  However, since i have not personally used these, my comments remain
somewhat less credible.
I wonder if there is a specific name for these connecters so i can check
them out on Eham.net or find others who have used them for long periods of
time in heavy duty applications.
73
Colin, V A6BKX