His core point is quite valid. The point of the burndown shouldn't be to drive a team towards focusing on the team's ability to match a perfect trend line. This is something I totally agree with. I've seen teams with perfectly straight lines on their burndown and I've learned that this is a big flag! That being said, his following sentence:
I believe that the underlying goal should not necessarily be about staying below the estimated time line in a burndown chart (although this would be nice)...might set the wrong tone for a newbie to agile. I wanted to address that here.
Joe Blotner captures this well with the following statement:
Scrum doesn't solve your problems, just make them visible, so you can solve them....which I'm sure that Jack would agree with.
But... I want to state that I think the main goal of a burndown IS to trend downwards. This isn't the same as staying below the estimated line, but I want to be clear... if the trend isn't down, then you are going backwards. As a business person (PO), I would not accept a burndown going up or flat too long. This is a sign that I'm spending money and there's no sign of progress (both in uncovering all the unknowns and in making progress). I'd almost prefer seeing the line spike up and then start working back down so I know the problem is behind us. A flatline always triggers me to ask "but when will it end?"
That being said, if this is what was happening before agile, then Joe is correct. Agile has helped you focus on this and now you can try and fix it.
Little nuances I know... but I wouldn't want to see a new scrum team looking at their burndown and saying... "eh, that's okay for now... let's figure it out in a few days (or at the end of the sprint)."