Put it this way - from what I hear, the two-day long lab test has about a 15% pass rate. Most people don't make it to the second day and a lot don't even make it to lunch on the first. It's one of the toughest tests in the industry. If there's a harder one, I've never heard of it.
I've had employees who have been doing hard-core networking (for big companies like AT&T and Boeing) for many years study 20 hours a week for 6+ months and still bomb the lab. The written isn't that hard, but the lab is a killer.
So far as I know, of all the professional networkers here, I don't know of any who have their CCIE and we're a pretty hardcore bunch, many who have been around since the beginning of real modern networks.
At this point, I consider myself to be pretty well-versed with most Cisco switching and routing hardware and wouldn't DREAM of presuming to take the CCIE, even the written.
- G