I'm pretty sure my current mechanic did not miss this, but I cannot say for sure about the one prior to him. The last time I changed the ATF was in early 1999 -- about 30,000 or so miles ago, so I am about due anyway.
This problem may have actually begun last fall when I noticed a barely perceptible surging on harder acceleration. I also would notice fluid leaks from time to time, but they were so small and infrequent that I did not take them very seriously.
Prior to adding fluid earlier today, it would take a few seconds for gears to engage after shifting (when stopped). Now the instantanous lunge forward or backwards has returned, and hard acceleration is smooth, with no trace of surging.
This may also explain the reduction in mileage I have been seeing lately. Normally, I get about 440 miles per 16 gallon tankful (not counting the reserve). That dropped to about 360 miles in December, probably due to torque converter inefficiency. I expect that to return to normal after today.