Yes, I also think post sim is very important,
because it can check whether the timing script is in mistake..
1) Pre layout (unit delay) is also important;
because sometimes, the formality can miss
some mismatch; I have meet this case for one time.
2) Post layout is to check whether the timing constraint s is put correctly.
So, also necessary...
What I think, do not rely on one tool...
The EDA vendor always say their tool is perect..
But when the problem generate, just hmmmmm....
Maybe after short time, one new version is there,
welcome to download...