My gut feeling is that there's still good value in frequent demos/checkpoints/etc. It does create a sense of urgency to complete tasks and lets the owner know that progress is really being made.
Besides undercommitting for the sprint, I've seen a lot of point inflation. Developers start padding their story point estimates to allow for extra time.
The worst case I ever saw was a team of five developers breaking down a feature request into very small stories with total points that would require the whole team's workload for two sprints. I completed all those stories by myself in three days. I'm good, but not that good. I suspect the team was so tired/afraid of being admonished by the Product Owner, they just kept padding and padding their estimates.
Of course, no one bothered to look at the cause of the problem behind the developers massively over-estimating required effort. "The Process" is always right, and the people are always wrong. Isn't that the first principle of the Agile Manifesto (sarcasm intended)?
