I also stopped using after 0.3 and tried it recently again to speed up some NLP code in Python3 and it hasn't been faster than Python3. Back then I didn't like the poor support for pyjulia, slow string processing, people using unicode symbols as variables, module import system, lack of libraries for more obscure NLP algos, and startup time. I know these aren't major issues for the core users of Julia, but these were my concerns.
The way I wrote the current code in Python was abusing sets and dicts a lot to take advantage of those fast data structs. Rewriting in Julia was fun because it was different and because multiple dispatch is fun.
However, it was roughly the same speed as Python. Ended up sprinkling some Cython on top of Python and resulted in 10x speedup. Didn't take much time to add types/pass pointers instead of strings to functions. I am not at all familiar with C++/Cython.
I think even if they speed strings/dicts up by a lot, there seem to be lots of breaking changes between releases so I wouldn't try it for something big.
I think if Julia is to succeed in the near future in the same way Python is successful for data science, it needs to be more usable for general tasks. Things like web servers, fast JSON parsing, maybe static binaries or easy parallelism. Basically, some more selling points. So far, for me personally Python is faster and easier to read for most of the things I write. At least given comparable amount of work.
A LOT has happened since then. For such a young language which hasn't even reached version 1.0 yet you can expect a lot of changes still.
You should seriously try out Julia again. I think it really works well now. I used to have a lot of issues with it before. Stuff would break, slow startup times etc. Today I don't really have any complaints.
Ok I got a few small ones. The limits on the ability to redefine stuff as you develop in the REPL can be a bit cumbersome.
0.3 was quite some time ago – string performance was certainly a problem back then (an acknowledged one). String performance on 0.6-alpha, released last week, is very good. It should now be at least as good as scripting languages that have traditionally focused on strings (Python, Ruby, Perl). There are a few more tricks we could do in the future that could make this even faster, but they involve a fair amount of GC trickery, so we'll have to see.
How is string performance doing?