I feel very strongly about the benefits of developing software using Agile practices. My experience with them started when I was running a software company called Sheer Genius and we found we needed to be nimble and be able to adapt to changing requirements quickly and without financial loss. This led us to try a lot of different things, including a new way of developing called Extreme Programming. In fact, we adapted XP, getting rid of some of the more strict rules such as pair programming, only using them when it made sense. What we ended up with is actually very close to what is now known as Scrum. This was so successful that after I sold the company in 1995 I advocated it with every one of my consulting clients and at every position I've held since then. It wasn't always the best way of doing things and my understanding of Agile frameworks has grown. I now advocate Scrum, Kanban, or a mix (Scrumban) for some projects. There are also some projects and development activities that will not benefit from agile practices at all.
I realize that, having also done traditional project management, there might be some hesitation about my commitment to agile practices. After all, traditional PMs approach projects from a command-and-control mindset. I've always been a non-traditional PM. I have always believed that teams can do better work if they are self-organizing and if I adopt a more servant-leader role. My first meeting with a new team will usually have a conversation about this. I never push Scrum or any other agile practices on anyone I work with. The team has to decide this is what they want to do. In fact, most of the variants I've observed are due to decisions the team has made to modify some of the practices.
Bottom line is that I know the PMBOK way of doing things and have never been a strict adherent. There is a lot to be learned from traditional project management but I believe that true innovation, creativity, and productivity are unleashed when the team is empowered to lead with a ScrumMaster helping remove obstacles and making it easy to focus on what they do best.