Here are two recent observations...
(Aside: It may have been fixed by the time you read this, but you have to uninstall the V16 Compiled HTML Help (CHM) before installing the V17 version... no biggie once you know about it, and it will be fixed.)
Apparently, we are lucky to have the CHM at all, in V17, but that is a discussion for another day. One example of "less functionality" (the only example? one hopes) is that individual V17 CHM topics no longer have context-sensitive links at the bottom of the page to the corresponding page in DCX.
Soooooo, we're all going to be using DCX more often, and not just because it has many improvements, which it does.
But... DCX is slow slow slow slow slow. If that is being worked on, great! ...carry on!
Making DCX faster should come before other improvements.