I'm becoming increasingly convinced that, to be successful, a team's agile practice needs to largely fly under the radar of upper management.

As soon as upper management catches wind, you'll need to justify every little process flow change to them, or they'll start demanding regular reports with burndown charts and plots of velocity over time and crap like that. At which point, you're done. Things officially suck forever.

That isn't to say that I think Scrum coaches and whatever have no value to offer. I've done a 1-week Agile training course, and I thought it presented some really great ideas. But their potential value is severely undercut by the fact that there's no way to bring one in without attracting the attention of the mothership.