Bill,
Ask the customer for data  on the (a) process, (b) solder joint
quality/reliability, (c) solder pot maintenance and (d) guaranteed gold
thickness, and he will back off......( just kidding).

Technically - gold in solder joint should be avoided in general. 1-3
micro inch gold will be dissolved during wave solder if wave contact
time is 5-8 seconds. It will depend upon wave width, conveyor speed and
whether the machine is single pot or dual pot.

Now 1-3 micro inch gold will be porous, especially on PTH copper which
is typically rough, so you will have exposed copper. Again depending
upon how long you store your PCBs and in what type of environment, there
may be solderability questions.

Finally, controlling gold thickness is tricky, have seen it vary upto 30
micro inches. This much gold will cause brittle joints.  People set up
processes to remove gold from leaded components to avoid this type of
problem. Also consider the case when you have to wave solder a gold
leaded pin-grid-array which will add to the gold dissolution problem in
PTH joint.

pratap
www.rampinc.com

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