One thing for certain is the Bengals have made steady improvement over the years and I feel it is directly correlated to Marvin's progression as a coach - not in terms of his coaching style/approach or talent selection, but the increasing development of the aforementioned characteristics.
Clearly, a major key to the Bengals' success in recent years has been the improvement of scouting and decision-making in the drafts. No doubt we are bringing in better talent - but there's more to it.
Perhaps one of the more notorious hallmarks of the Bengals organization has been the ever-enduring commitment to rolling the dice on character-issue players. It has plagued the franchise for years as we've witnessed cancerous players ruin the locker room and promising talent self implode. Well... we are still drafting and picking up reprobates, however they are contributing without hindrance or self implosion.
Think of some of last season's players who have had character concerns: Andre Smith, Carlos Dunlap, Vontaze Burfict, Pat Sims, and Pacman Jones. Andre Smith has emerged as one of the top RTs in the NFL. Dunlap is arguably the most gifted and dangerous pass rusher we have. Burfict is without question our most talented LB and potential All-Pro. Pat Sims eventually became a major force in the middle who proved our run defense suffered without him. And Pacman has been a critical factor in the nickel package (which was used 50% of time last season). Imagine if Marvin didn't roll the dice on these guys... we most likely would have relied on either Jason Smith (eventually released by two different teams), Eugene Monroe (average at best), or Anthony Collins/Dennis Roland at RT, the innocuous pass-rush of Geathers/Gilberry on the left side, Vincent Rey or Dan Skuta at WILL, Jason Shirley as a short-yardage DT, and 33 yr old Nate Clements as the nickelback this past season.
Ask yourself this question: Without Smith, Dunlap, Burfict, Sims, and Pacman, would the Bengals have even made the playoffs in either of the past two years? I doubt it. And collectively, they only cost us one 1st round pick, one 2nd round pick, and one 3rd round pick.
Earlier in Marvin's reign however, there were players we picked up (i.e. Odel Thurman, Chris Henry, Ahmad Brooks, and Terrell Owens) who ultimately did implode or bring cancer to the locker room. What has changed?
Marvin's authority, tenure, respect, and clout. Contrary to other teams where players often have leverage over their coaches, Marvin is clearly the man in Bengal realm. If there is one thing to be said for Mike Brown, he is loyal. And he has made it clear (despite various fan & player bickering over the years) he is loyal to Marvin Lewis.
Beyond his authority (which has been extended to a defacto GM role), tenure, respect, and clout, I think Marvin has inherited a bit of a fatherly role to many of the players as well. I think he has an uncanny ability to provide mentorship to players while still holding them accountable and maximizing their potential. And this extends beyond the field. When players develop a more personal relationship with their coach and teammates (as I believe has been happening with this team), they possess a higher commitment to staying out of trouble off the field in order to avoid letting the team down. Yes, it is professional sports and ultimately money is the most important incentive - however it isn't the only incentive.
So, in current application... when I see a talented guy like Tyrann Mathieu whose stock is dropping due to character concerns, yet Marvin has expressed interest in him, I say let Marvin take him under his wing. Most other teams, he'd be a cancer.