Here are my $0.02 worth:
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Plotting must be unobtrusive. It is unacceptable to have to wait for many seconds or minutes before DataFrames or Plots load and processing transitions to your own code.
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Debugger must be available.
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It must be easy to call Julia from Python or from R.
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Discovery of packages must be easy.
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There must be a solid selection of success stories and inspirational projects in Julia.