I hiked out into the cold clear night at about 07:30 UTC tonight and was rewarded with a nice view of Endeavor as she climbed uphill following her launch at 07:28 UTC.
She was a lot brighter than I expected - easy to see under the bright skies within Boston city limits. She gradually increased in brightness as she passed from southwest to southeast, and then I saw rapid flashing - I am guessing main engine cut off, external tank separation followed by separation maneuvering.
T.S. Kelso of celestrak.com made a very nice "scenario" describing the launch using the viewer software from his company AGI. I used it to help plan my observation - check it out at http://celestrak.com/events/sts-123-launch.asp. It is worth the gigantic (100MB) download. I encourage all who live on the US East Coast to go out during the next night Shuttle launch and look. Great fun!
-Joe KM1P