Scrum/XP has worked for my team. Four years in, we deliver better adapted solutions with higher code quality.
What I love about Agile is that it acknowledges what’s hard and treasures what’s valuable. There is inherent complexity in modeling partially understood and fluid problems. There is deep potential in talented people rallying to achieve a goal.
However, Agile is not the only path to valuable software. As Stephen McConnell and Barry Boehm say, it’s all a matter of the appropriate tools for the appropriate context. Different levels of planning, description and formality have their place.
The only way to know whether a practice works for your team is to learn it (seek mentors), apply it with discipline, and track your performance over an extended period of time.
The infuriating thing is many shops don’t think deeply about what they do: “The Demise of the Waterfall Model Is Imminent” and Other Urban Myths
The value of any practice is really doing it.