What are (were) the most difficult parts of D?

[Ola Fosheim Grøstad]

On Wednesday, 11 May 2022 at 05:41:35 UTC, Ali Çehreli wrote:
> What are you stuck at? What was the most difficult features to 
> understand? etc.

Also, if you intend to use the responses for planning purposes, 
keep in mind that people who read the forums regularly are more 
informed about pitfalls than other users. Forum-dwellers have a 
richer understanding of the landscape and probably view the 
feature set in a different light.