We have had some methodology panic. Not so much disagreements, but more:
em, we have to release this in a little bit and we have to collaborate more so we better agree on how we are going to work together now so we can deliver and not look lame/dumb/hand-waver-ishtype of stuff. We are transitioning from doing a lot of throw away semi-functional POCs where collaboration was optional to building 1 skeleton system where we must collaborate heavily or we will slip.
These types of transitions are tough. But if they don't kill you, they only make you stronger.
You can be on the best team in the world (I actually think I am on one of them - no joke) and until you have been through the ringer and shipped something with that team, it doesn't matter much what you have done before with other teams. You have to make it work with this team. It can be hard to get the rhythm building - especially when so much has to be bootstrapped to get that first story tested and working.
I have been using Scrum for quite a while - at least 5 years on and off (mostly on). I like it because it is easy. The teams I have been on that have used it were always successful enough - mainly because all Scrum really says is you have a backlog, a sprint/iteration planning meeting, a daily scrum meeting, a sprint retrospective meeting and you have short iterations where you can course correct.
Within Scrum I have been a part of various analysis approaches. I have been a programmer / analyst and have been on teams that have had dedicated analysts who do insanely large Use Cases. Now I am on a team with 1 analyst who just churns out epics /stories like they are going out of style. She "gets it". I like people that "get it". I have been helping here prioritize / size the backlog lately.
On this project we are amping it up a bit and embracing things like Epics, stories, heavy TDD (Test Driven Development), and gasp ... a little pair programming (strictly voluntary for us). It really helps when you have an iGel Ninja around. You don't even have to listen to him talk - you just watch his hands and you understand (mostly). Come to think of it, we have 2 - we also have an Irish one. He isn't so much with the hands, but when he is the smoothest swearer I have ever met. It doesn't offend anyone when he does it even if it is a f-bomb. Dropping an occasional f-bomb is crucial to iGel success IMHO.
I have tried and failed too many times to count at TDD. But this time I am on a team that has the will and desire to succeed. I know many of the things that make it fail or rot on the vine. It basically comes down to discipline and no broken windows.
Our wiki is quite helpful in all of this as usual. I would jump out the window if someone took the wiki away.