It is Doug Marrone day on the site. We got the boys over at The Saints Nation to talk about Marrone's work in The Big Easy. Check it out and tell a friend.
1) What were the pros/cons for Marrone when he was the OC for the Saints?
Pros: as good as there is understanding/teaching protection schemes, really developed the Saints o-line quickly into an elite group. Jon Stinchcomb called him the best coach he ever had. Learned from the best in Sean Payton
Cons: wasn't a traditional OC because Payton called the plays. It was basically a glorified title, he was really the offensive line coach.

2) I know Payton called the offensive plays for the Saints, but what do you know about Marrone's impact on the gameplan?
He had some input for sure and at the time he was Payton's most trusted assistant. Outstanding in preparation, so his opinion was always valued, but it's said he was never given more opportunity perhaps due to lack of creativity.

3) Normally, assistant coaches borrow some of the traits from their head coach, do you see that with Marrone?
Not necessarily. I think he's his own man, very legit and has his own set of principles. That's why Sean valued him, he brought something different to the table. But there's no doubt his time w/ an offensive mind like that was beneficial and he picked up some things.
4) What sort of offense do the Saints run? I read Marrone ran the same type of offense at Syracuse.

Pass heavy offense with heavy rotations. The Saints are 4 deep at RB, all w/ different skill sets, 5 deep at WR, also very different. Then they just rotate them in and out mixing up personnel as much as possible to confuse defenses and create mismatches. This requires numerous diverse skill players w/ different assets to pull off, along w/ an accurate QB. But it works. 
5) Did you see a  difference in the Saints offense when Marrone left?
No. In fact it got better. I attribute that to the core group understanding the playbook more due to experience with it, though, not Marrone leaving. That said, Carmichael has been solid as OC showing good creativity and play calling ability. Marrone leaving wasn't a big loss, but that's not to say he wasn't valued.
6) Do you know how Sean Payton viewed Marrone?
As mentioned before, he trusted him greatly. There's a reason he got the Cuse job, he was Sean's top guy at the time.
7) Do you think he will make a good headcoach?

I'm not convinced he was that great with Syracuse, though its a tough job to do well in. I think he's a good teacher, good leader, high character, and he'll bring in a good plan. Beyond that, he'll need the right personnel and that's going to take work. The coaches are only as good as their players and while the Bills have some pieces, I think their roster is currently subpar.