My entire experience has been: good management + talented developers = success, and bad management or untalented developers and it fails, but it really has nothing to do with the methodology in play. I've seen (and been part of) hard core agile teams burning to the ground, and teams with no methodology be wildly successful. (And vice versa)
Agile bothers me because it generally aims to commoditize developers, and yet the best places and teams I've worked on always were they opposite: it was about finding the best way for each individual to work, and designing processes around the rhythms around whatever industry they were working in, rather than assuming everything should fit into 2 week sprints.
The best places to work adapt the process to the team.
The worst enforce a process on the team because it makes managing them easier.
The number of workplaces I've been in who equate the number of hours that people are in the office with their productivity, because managers could measure attendance easily, and had no idea how to measure actual productivity...
I took an organization that couldn't put out two releases a year to one that put out once a month, and the owner/manager complained bitterly and pushed new features into the discussion ON THE DAY OF RELEASE.
2nd level management had to constantly, repeatedly attest to the good that the tempo and structure brought to the organization and customers.