I am almost sure this is already known and safely in hand, but just in case:
We can now create checklists very nicely (e.g. by setting a parent node to the Action “mode”, which will turn its children into Info “mode”). And we can even have the info children organized in collapsible sublevels in the All Projects view. Excellent so far.
But when we see that checklist action on the Next list or Focus list there are no children at all, so it current really cannot be used as a checklist from any of those screens. I assume this is firmly in the plan to fix.
Also, when you complete (check off) a checklist item, the item now disappears completely from the checklist. In a way, maybe this is good, and consistent with how project tasks are dealt with, but the more common approach is to just show completed checklist items as grayed out and checked off within the checklist itself until the whole checklist as a whole is checked off as completed.