The problem with the first one is that what you are declaring is effectively a const pointer named 'a' to 10 consecutive memory locations allocated for the size of int. The second is a declaration of a variable-length array named a.
So, for example, you can't do this:
int a[10];
int b[10];
a=b;
You get a type error, or an lvalue error, because you can't assign anything to a constant.
Good point, but still, you can apply operator [] to a and b in some non-C dynamic language, which means the "int a[]" style is probably more relevant psychologically.
I agree that int a[10] feels more natural, though if the brackets are empty my only preference is that the language pick one or the other. Don't make "int[] a;" and "int a[];" equally valid syntax, but totally different semantics.
My main point is that this is a relatively cosmetic issue relative to the ability to use 'foreach' syntax instead of iterator objects and while loops.
There's clearly a market for some sort of a fixed C++ but not the Java/C# way. D tries to fill the niche, but it doesn't give a feeling of elegance or otherwise of something really new and unseen before.
Templates in D look like just a syntactically polished variation of C++ templates. Of course there are some new features there, but I don't see anything that can't be done with a compiler that is capable of evaluating some functions at compile-time. C++ can't do that, but my point is, why bother creating such a complicated template system for something that can be done the easy way?
Variadic templates: can be done with variant arrays and again, with smart compile-time evaluation if necessary.
So, for example, you can't do this:
You get a type error, or an lvalue error, because you can't assign anything to a constant.