Here's a non-exhaustive list of things that aren't working as they should. I'll keep adding to this list and update it with fixes when they occur.
Font Carts that don't work in CCR when using the Add Text Box feature.
When you add text to a text box using these fonts your text won't appear. When you press enter you'll see this symbol.
For now, to use the font on these carts you will have to add the letters to your mat directly from the virtual keypad.
Using Colors and Patterns to fill Cricut Shapes.
Update - this problem is now fixed!
When you fill a Cricut shape with a color or pattern from an Imagine cart you may find that there is a strip along one side that looks a bit warped.
Edited to add: I believe that Build 59 of CCR fixed this problem, but I haven't tested it out yet.
Cartridges not recognised by CCR when inserted.
Here I'll list the carts that CCR doesn't recognise: