Manu wrote:

Eg, I press '.' and the list of methods appears, and I skim through the
list and choose the one that looks appropriate, I'll choose receive, and
then I'll be puzzled by the argument list and why it doesn't work like I
expect, after a little wasted time, I may begrudgingly read the manual... I
personally feel this is an API failure, and the single most important thing
that C# gets right. You can literally code C# effectively with absolutely
no prior knowledge of the language just using the '.' key with
code-complete in your IDE. The API's are really exceptionally intuitive.

This is a big restraint to D's popularity. It's certainly a complaint I've heard from others. An IDE with intelligence might have been a luxury in the past, but it's quickly becoming essential to large project development. Things like hunting through poorly cross-referenced documentation just to find out how to convert a string to an int, then doing it all over again when you realize the same function doesn't go both ways is just a pain in the ass.