I saw this gem today when browsing company reviews on Glassdoor.
You should consider critically how difficult you found the interview process, and what that might mean for the calibre of your peers if you accept an offer.
What they are getting at is the idea of working for/with people that are smarter than you. This will push you into learning more and learning faster than you might otherwise do so. Extending this idea out to examining the interview processes of potential employers is a great idea.
See also I am a comet.