Will,
I think the most annoying thing for many or most users is the Persona Bar. The "old" control bar had it's logic, and things are completely different now. This is not a really big issue, I compare this to the change in MS Office from the menu to the ribbon bar. At first everyone I know said it is stupid (and parts of it were in Office 2007), but after Office 2010 they got used to it, MS made some changes in how and where to find the functions - and it turned out that the ribbon is easier to learn for beginners and more intuitive. The real problem is missing functionality compared to the former UI (e.g. disable pages).
Just some thoughts for a solution:
1) Let the user choose if he/she wants the Persona Bar or the Control Bar - at least just for a while, say in the DNN 9 and maybe 10 product cycle. There was always the possibilty to use the old Ribbon Bar instead the Control Bar in former DNN versions, why not let the user decide here as well?
2) Create something like this:
https://www.howtogeek.com/howto/16386... (the original animations provided by MS are not available online anymore, at least I could not find them, but this tool was really a great help!)
3) Add the missing functionality to the Persona Bar asap.
Happy DNNing!
Michael