Completely agree. dplyr is nice enough but the verbose style gets old fast when you're trying to use it in an interactive fashion. imo data.table is the fastest way to explore data across any language, period.
I strongly agree, having worked quite a bit in several languages including Python/NumPy/Pandas, MATLAB, C, C++, C#, even Perl ... I am not sure about Julia, but last time I looked at it, the language designers seemed to be coming from a MATLAB type domain (number crunching) as opposed to an R type domain (data crunching), and so Julia seemed to have a solid matrix/vector type system and syntax, but was missing a data.table style type system / syntax.
Julia v0.7-alpha dropped and it has a new system for missing data handling. JuliaDB and DataFrames are two tabular data stores (the first of which is parallel and allows out-of-core for big data). This has changed pretty dramatically over the last year.