I just went out tonight (spotted a Leonid!) and noticed Comet Holmes has vanished, well it hasn't vanished it is still there but I couldn't make it out among the light pollution with just my eyes after a few minutes of dark adaption. I wouldn't call it an easy naked eye object anymore.
Part of the trouble comes from its angular size, it spreads the light out over an area larger than the Moon which makes it difficult for our eyes to detect. So make the most of this now binocular object before it fades any further.
2007 has been a good year for comets, we had McNaught in January, which was so bright it was visible in daylight (although I failed at spotting it). Then Comet Holmes, which put on an amazing show considering it is outside the orbit of Mars. When a little snowball about 3 kilometres across blows off a shell of material around 1.5 million kilometres across, becoming largest object in the solar system (yes larger than the Sun) you can't help but wonder how awesome it would be if it wasn't half way across the inner solar system, but was a little bit closer to home, what would really be good was if the Earth passed through all the ice and dust its blown off, then we'd have a real display. Oh well maybe one day.