re: Very exciting
I agree awesome accomplishment!
There were a few outburst observed of Tempel 1 prior to impact but no luck in capturing a outgassing with the probes camera as you said.
Outgassing article:
http://www.nasa.gov/mission_pages/deepimpact/media/deepimpact-062805.html
Haven't heard of any naked eye brightening observations but there were detection's from ground based telescopes of a brightening image of Tempel 1 after impact.
Articles and photos: http://www.faulkes-telescope.com/scied/deepimpact/deepimpact_new.html here are the best and there are some from the amateurs too at: http://deepimpact.umd.edu/amateur/gallery.cfm