It really depends on the kind of project you're working on. Some modern Agile authorities (see Balancing Agility and Discipline: A Guide for the Perplexed) will

It really depends on the kind of project you're working on. Some modern Agile authorities (see Balancing Agility and Discipline: A Guide for the Perplexed) will tell you that you should tailor the process to your specific requirements. They would never recommend that you use XP for the development of life-critical software that has hundreds of engineers working on it. Agile is born from rapid prototyping and makes a lot of sense for that environment. If you're doing work where one day you might be developing one thing, and the next day you might be working on a completely different product altogether, then reducing the cost of change is the only thing that makes sense. If you're not, then don't use pure agile, it doesn't make that much sense. There's obviously an issue with one size fits all approaches to agile, and as agile matures people realize that more and more, instead of forcing you to do everything by the book. The point is, as you get more and more experience with driving software projects, you need to be smart enough to understand what will make sense and what won't.