A bit late to be answering this question, but I just found this Yahoo!
group while surfing around.
My name is Sue Johnston, and I believe I have the current supported
record on the JMT (3 days 20 hours from Whitney Portal to Yosemite... 3
days 15 hours 32 minutes from the summit of Whitney). I hiked the trail
from 8/24 - 8/28 this year.
If you're interested, I have a report, gear list, etc. on my site:
It was great fun!
Michael Popov has the unsupported record to the best of my knowledge.