Looking over the current O'Reilly demo app, there are a couple of changes that I find make it less usable than the original 2.0.x I had been working with, and one of which may be a bug.
On the Sessions list, it used to be that the room name displayed to the right of the session name. This made the scroll list shorter, which I find is better, and appears to be the result of the session title/name container to no longer be inside a div with class x-list-item-label. Changing ".x-list-item-label > .session" in app.scss to ".x-innerhtml .session" seems to fix the issue.
The one that has me stumped however is the session detail page, which now uses flex. In the earlier versions, you wouldn't have separately scrolling boxes (i.e., top for session info, and bottom for speakers list). The content was displayed in what essentially amounted to a single scrolling page. I've tried to modify the code to no avail, even pasting in the old demo's code in view/session/Detail.js. Any idea how to go back to all the content being displayed with a single page scroll?
Looks like the examples were updated to get them working rather than working like they were before. The second issue with the session detail page is a result to a change in the list implementation from 2.2 on lists no longer auto grow and need some kind of sizing. You could set scrollable to null or false on the top container that way only the Speakers list scrolled. Or you could docking both containers to the top of the list. Like in the following example: https://fiddle.sencha.com/#fiddle/2h4
I will submit a bug report for this issue.