"A faint glow in the constellation of Cancer should become one of the brightest lights in the sky towards the end of 2013, if astronomers' predictions are correct. Depending on how big that tail gets, it could shine brighter than the full moon in the evenings."
"How bright? Various estimates have set the brightest magnitude at -10 to -16." In comparison the sun is magnitude -26 and Hale-Bop was -1.
The only comet I remember seeing was Hale-Bop and was too young to appreciate it. Hopefully this one puts on a spectacular show!