Stage Gate is like Gold Digging and Waterfall is for building railroads.

Organizations create governance that impacts productivity.  The leaders of the company need to have insight into the decision making process, and provide guidance to align with strategic planning.  One area that works is applying a decentralized stage gate process.  This is a valuable asset that empowers self motivated teams to report success and resolve their own roadblocks.  The group decides what should be handed off, and how to self-correct problems without having a command and control compliance officer setting timelines and milestones for them.  

Stage Gate process were established to filter important ideas from strategic leaders of the organization.  This is similar to mining precious metals, where you have lots of byproduct to process. The gates or cycfines  provide them the resource and financial backing required so they are successful.  In many cases, this has become a paperwork exercise, and at worst a fiefdom where centralized organizations are making strategic decisions and without the backing and support of the senior management team.  

Stage Gate Processes should be Engines of Innovation, since this drives the discourse to align the strategic vision of the company with the tactical implementation.  The discussions for steering committee should focus on prioritization and support as compared to compliance and status.

Agile methodologies create a framework for accountability.  Based on a inclusive strategic planning process, teams can be guided on what will have the largest benefit to the organization.  Once you have the governance team as cheerleader and supporter, the results bread the success that make people want to come back to work every day.  

I am always engaged in a waterfall vs. agile conversation when talking about stage gate milestones and timelines.  My augment is agile allows you to learn and be lean in your approach.  Waterfall is only required when you know exactly where you are going from the start.  I imagine the architects of the railroad had many challenges, but the notion of where they were going to lay the tracks was not one of them.  We are not building a railroad, we are building complex services that changes daily with customer input and feedback.  

Expect honest not accuracy

As a Scrum agile practitioner; I spend downtime thinking about simple ways to say powerful things.  I have been setting my team expectations on two things, Transparent and Proactive.  Adding to the list is expecting honesty in estimating.  I did not say accuracy.  All humans are poor estimators.  I would rather have honesty than accuracy.  Better data is better forecasting.  I see new words to line the workplace; transparent, proactive and honest team members can conquer the moon.