A few things that I've bumped into over the past couple weeks since I bought CC3...

1) Symbols - the relationship between symbol styles, symbol catalog settings, FastCAD symbol catalogs, the actual PNG's themselves, and the UI that interacts with all those objects is extraordinarily unintuitive and almost completely undocumented. If you want to do anything more with symbols than use the premade styles, you're going to need to spend hours basically reverse-engineering the symbol system from the vague clues you get out of the UI's behavior. I really think this is one of the most user-unfriendly subsystems I've ever seen (coming from a UNIX nerd) and is absolutely screaming out for documentation.

2) The various trimming and selecting functions are pretty foreign to most people, I'd guess. (They were to me, at least.) These are decently well-documented in the Help files, but it would be nice to have a single tutorial bringing the info together with some examples.

3) Sheet Effects are scantily documented and prone to strange interactions, but also very important if you want a good-looking map.

4) A short tutorial on editing, combining, and exploding existing entities would be helpful. This is all in the help, but again it's spread across a lot of topics and would be much more useful all in one place.

I didn't find the basic use of sheets and layers to be very problematic compared to many people. I have to wonder whether they actually followed the built-in tutorial, as it covers those topics quite well.