I too have the same problem.
1999 SVT with 31,000 miles on it.
I took my to the dealer about 6,000 miles ago, and they couldn't reproduce the problem. In fact, they told me their tech shift the car 160 times, and found nothing...

Yeah right!
I haven't taken it back since. I am a bit worried though, because some SVT owners have said the new tranny is just as bad if not WORSE than the old one...
Keep us posted.
Patrick