asterisk users - Jul 2006 - Do zttest results matter without telephony hardware?

I'm running an asterisk server that uses an IAX2 trunk with our voip
provider for its PSTN gateway.  We have no telephony hardware in our
server.  We are consistently getting 99.975% or better when we run
zttest.  I have heard that this is bad in some cases, but I'm
wondering if it matters, since we are not using any telephony
hardware.  Can somebody please clear this up for us?  Do zttest
results matter when you don't have any telephony hardware in your
system?

We think there may be some call quality issues with out provider, but
whenever we report them they turn around and say that our zttest
results are bad and that our server is probably the source of the
problem. However, our calls between extensions are superb, so I can't
believe that our server is to blame, since only calls to and from the
PSTN seem to have problems.

Thanks in advance for your time.

Carl