1st report: Good thus far... Took two 45 minutes trips this weekend on a route that has me at 40 to 50 mph the whole trip ... this route would always experience the shudder at least a hand full of times.... But after the flush and Dr. Tranny, no shudder this weekend.
Don't want to jinx it, but so far so good... not sure if it's the flush or the Dr. Tranny, or both... but who cares...
If it took care of the problem for < $100 instead of >$2K, it was worth a try (BTW, the book time for a V6 is 12 hours, list price on a TC is $1250, but you can buy from Toyota dealers online for ~$800).
And yes I did use OEM Toyota WS ATF... did 3 flushes... If I were to do it again, I'd flush a couple more times; the fluid was still a little dark after 3 flushes... Not nearly as bad as the original fluid, but not nice and bright red.
My initial thought was that Dr. Tranny was a joke... but it's not a joke, it's a real product
Amazon had nearly a 1000 reviews and the vast majority of folks said adding it totally eliminated or dramatically reduced the shudder.
Special thanks to cisco636 for pointing out this inexpensive potential fix...