I get these things every five years, thanks to colon cancer running in my family via primary relatives, so I know they’re worthwhile. They don’t hurt, thanks to the drugs you get. The worst thing about them is the awful preparation fluid you have to swallow by the gallon. Tastes like motor oil.
But I really must demur when some bloggers, including the vaunted Instapundit, say they are foolproof at discovering colon cancer. My father had them for years and they didn’t save him. Maybe it depends on the skill of the doc. That would figure. That’s why they’re called medical "practices."