Unfortunately, they are often best viewed from the opposite hemisphere from the one in which you live, or are clouded out. It doesn't help that about half of them put on their best show right around sunrise, so unless you get up that early, you aren't likely to see it. I've seen several telescopically, but I saw one in the mid '90s (I can't recall whether it was Hale-Bopp or Hyakutake) that was actually quite spectacular.

I set the alarm for an hour before sunrise and set up my scope to take some pictures of it, and early risers on their way to work at my apartment complex came by and asked me what I was looking at. When I pointed it out, low on the horizon, brighter than first magnitude, and with a mother-of-pearl tail stretching across 3 degrees of dawn sky (six full moons), they freaked out.

I can see why in the olden days, when people were quite familiar with celestial phenomena and there was no light pollution, they caused fear and panic. Comets show up from nowhere, very mysteriously. Farmers trudging to the fields around sunrise would watch this gleaming scimitar of light rising just ahead of the sun, without any warning. And it would be visible for several days, slowly moving across the familiar constellations. No wonder people were terrified of them.

I suspect none of my neighbors would have noticed it if I hadn't been there to point it out. Most people don't look at the sky any more, they just don't care. To them, it always looks the same.

It was the most beautiful thing I've ever seen in the sky, with the possible exception of the Southern Milky Way from a ship at sea.