Well, I'm hopefully at the end of my tranny problems - I pick up my car with a rebuilt tranny in a couple of hours.
I had a similar problem that you are describing, and can tell you that by adding some Lucas, and then changing to RedLine synthetic ATF, I was able to see some improvements - and I was able to drive the car (with it getting progessively, but slowly, worse) for over 15,000 miles before it actually starting "slipping" in gears (at which point I was afraid it might leave me somewhere, so I had it rebuilt...)
For the record - you can find places that will rebuild these units (or exchange your damage unit for one of their rebuilt) for about $1300. I got real lucky (I hope) and found a reputable garage (that does tranny's only) and they did it for $1200 (complete, including R&I tranny in car).
-David