Re 2: Yes, but most of the language is geared towards 1-based indexing, e.g. ranges like a:b being inclusive at the right. Hence, using a zero-based variant of array makes only sense if your code really really profits from zero-indexing.
Btw, the question should not be "is zero-based slower"; I know that julia has zero-cost abstractions. The question is whether is is faster, because of the avoided decrement instructions for the underlying pointer arithmetic: say, M=Matrix{Int64}(4,N), then @inbounds x=M[i,j] corresponds to x=unsafe_load(pointer(M), i + (j-1)*4). And the internal C code needs an extra decrement on i, because array data pointers use the C convention of pointing to the first element.
Re 4: This is a problem with discoverability and dependencies. Say, my code needs a heap-queue.
Sure, heaps exist, e.g. in datastructures.jl. But there is no canonical documentation / default choice in the base language, like e.g. heapq in python.
And if you want to figure out how to use custom orderings for your heap you end up reading the source code of all 2-3 heap implementations in datastructures.jl (which use different incompatible APIs), because the documentation fails at providing examples. Older julia versions came with heaps included.
Re 3: The REPL is not everything. By all means, define a global name mangling scheme that (with default options) symbol-names should be latex-displayed in the REPL or ijulia. I mean, when using a mono-spaced font you don't want to see a greek sigma in latex either! You want the code, i.e. \sigma, and you want someone (not yourself) to write a word-processor that inline-displays weird characters for your grandma.
Don't understand me wrong, I like julia; it is just that every single "mostly inconsequential" / matter-of-taste design decision pisses me off, whereas the really important parts are awesome.
Re 1: Maybe I haven't written enough fortran in my life, but both python-significant-whitespace and C/java-style curly braces make a lot of sense and are very easy to parse and highlight (for text editors). But sure, I understand that this is matter of taste, and very cosmetic.
Bonus problem: By default, multidimensional arrays access is such that the first index is fast for iterations. This is different from C layout, and means that A[i,j] corresponds to A[j][i] if you switch out Matrix and Vector{Vector}. I know that fortran did it that way, and I think this was a mistake in fortran already.