What are the real advantages that D offers in multithreading?

[w0rp via Digitalmars-d]

The most important thing D does, which is fundamentally 
different, is that variables are thread local by default, and you 
must opt-in to variables that are shared across threads. 
Immutable data can be shared implicitly, because there are no 
writers. This means that if you keep only a small amount of 
shared state, it should be easy to track down what could possibly 
be affected by multi-threading issues.

I haven't ever used synchronized classes myself, but it's 
probably a way of preventing mistakes where you synchronize some 
methods, but not others. You can also use synchronized {} blocks 
to introduce some recursive locking for a series of statements. 
So you could put that inside of a class method.