With all due respect to you posters, Ruud probably knows way more about Pelini's defense than both of you put together.
To use the cooking analogy, there's a lot of edible meals you can cook without knowing the details. But the difference between edible and a culinary delight is all about the details. I think there's a lot of degrees or shadings to how complicated the defense is. There's been players who got on the field quickly (Glenn, Gomes, David, etc.), so it's not as black and white and easily digested of a topic as we perhaps try to make it.
Cody Glenn started out of sheer necessity. We literally had nobody else to fill his role.
Gomes didn't start until the Texas Tech game in 2009, the sixth game of the season. The Missouri game the week before - during which he had a key interception - was where it "clicked" for him.
LaVonte David is a freak of nature, but even still the only reason he started as early as he did was due to Fisher's broken leg. The plan was to bring him along slowly, a la Dejon Gomes. David would succeed in any defense, though - the guy just has a nose for the ball. Despite that, Bo himself will tell you that David often did things wrong in the early going. It was just his crazy ability that made it all work out.
Both Gomes and David were JUCO transfers, guys you don't recruit unless they can make an immediate impact. It's rare to see a Mo Seisay who gets recruited but who doesn't see the field much coming from JUCO. But those situations happen, and you can't look at Gomes/David without looking at Seisay as well.
There are far more examples of guys taking the slower path under Pelini than guys getting on the field right away. It's not a coincidence - it's because the intricacies of Bo's defense take even football-smart guys time to fully grasp.