Background: In 2006 I contracted with a large company which had adopted Scrum cold turkey just months before I arrived. The company hoped Agile/Scrum would save their huge enterprise software product. Of the hundred or more programmers there, I worked closely with a team of about a dozen for a year, observing and participating in their Agile experiment.
Summary: I believe Agile helped more than it hurt. By the end of the year, the team could consistently estimate and produce features, whereas previously their productivity was rather erratic.
Implementation: Since this was a large organization and a large product, the project ran as a "scrum of scrums." There was one scrum master for about every 15-20 developers and these teams were often divided into smaller, closely working scrums of about 6-8 people for an iteration. Teams were largely independent, could adjust their own iteration frequency (1 month down to 1 week) and were given lots of flexibility to implement agile as they saw best. The company regularly brought in Agile coaches (such as Object Mentor) to help train the scrum masters, teams, and management.
Obstacles: Plenty. Some of them related to Agile, some not. In no particular order, here are some lessons learned:
The product backlog was revised way too often in the beginning. Eventually, the team and management took several days to go over all the features, estimate them, and prioritize them. It was a big hit, but it helped tremendously. Lesson learned: get your product backlog in order early and keep it maintained. Product owners must have a clear idea of what they want.
We lost time experimenting and dealing with fads and hype. When you start, you have no way of knowing if you're doing things correctly. There's temptation to constantly fiddle with the agile process taking the focus away from the product. Lesson learned: having an experienced Agile coach does help reduce this learning curve. There should always be someone pushing back on any experimentation. Limit the number of "spikes".
A good scrum master is invaluable. Certainly in the beginning, it's a full-time position.
It takes time. It took several months before the team started to be comfortable with the process.
Pick your battles. Some programmers will be understandably skeptical and others will outright dislike and flight the change. Allow for some flexibility. For example, enforce the use of a product backlog and iteration schedule, but don't require everyone use note cards. Be particularly sensitive to introducing tools and programming methodologies such as pair programming or test first development.
Finally, keep communication open and manage expectations.
Good luck!
