Thanks for mentioning it. I almost always forget about Spyder. I'm not sure if that says more about me or Spyder.

Can't speak for Spyder, but one killer feature of RStudio is the ability to easily make C++ modules that your R project uses (RCpp rocks - you can ignore most of the annoying things about C++). They compile and link with zero effort. Also the ability to easily install modules. And browse documentation. And create projects in R or RMarkdown. Create modules, basic scripts, web apps. And publish things. And see your data in a spreadsheet format. And inspect all your objects/data/functions. All in one place.

Aside from RStudio, I love R's lispy/apl-ish semantics, and easy integration with Fortran/C++ (and a host of other languages, including Java, Haskell, Ruby, Prolog, Lisp, etc...).

I'm sure Python is great, but R is made for stats, is amazing, and RStudio beats every IDE I've ever used, regardless of language.

I don't believe I praised RStudio at any point in that commment and concern about a very realistic potential hurdle that Rodeo may face as it's codebase grows and matures =/= criticism. I have no issues with the speed of the current implementation (but do have a problem with its lack of features and numerous bugs). It's not a bad IDE, just nowhere near as mature as RStudio.