> Every team I've worked on that has switched from Kanban to Scrum has slowed down and never regained the previous velocity. Further, many of the promised benefits of Scrum (things like better insight and predictability about delivery rates) never materialized.

This has been my experience. I've seen more than once management teams happier with numbers and estimates that weren't met than actually getting software out quicker at an unanticipated rate.

They'd rather have estimates that they could yell about than revenue generating software through (presumably) happy customers. <shrug>