Here's an example of one frustration when I was trying to figure out this tagglytagging replacement.
I came across this tiddler on the main site
http://tiddlywiki.com/#tagging%20Operator%20%28Examples%29Here's what it displayed (with the first "try it" button clicked
[[task]tagging[]]
- → same as
[tag[task]]
Concepts task +[tagging[]]
[all[current]tagging[]]
- → tiddlers tagged with the current one
Now by this time I'd already figured out that just entering this
[[task]tagging[]]
didn't do anything, no frustration there. So having used TWC before I knew there'd be some hidden code in the edit mode and I saw this
<<.operator-example 1 "[[task]tagging[]]" "same as `[tag[task]]`">>
<<.operator-example 2 "Concepts task +[tagging[]]">>
<<.operator-example 3 "[all[current]tagging[]]" "tiddlers tagged with the current one">>
here's the frustration: I copied that into my personal TW5 and closed the edit mode and nothing was there. I tagged that tiddler with "task" and also created a new tiddler tagged with that tiddler the code was in and still nothing.
I think the brilliant part of tiddlywiki (non-linearity) is also a frustration source: A person can search for the functionalty and find it but not be able to use it because there's no clear indication of what I was supposed to have read already to understand how to use it. I did obviously figure it out, but ideally each instructional tiddler should say how to reproduce that function without assuming too much previous knowledge.
That said (because you asked), I'm still very happy with this new TW and look forward to exploring it!