R + RStudio + Knitr is pretty solid, but more than a bit clunky - write Markdown, intersperse R to your heart's content, and you can execute lines as you see fit.
I have very high hopes for an R + LightTable integration.
R + LightTable would be lovely. As almost everyone else, I use a gross combination of the R GUI (Mac), Emacs, and Sweave.
I am not a huge fan of markdown other than as a "with benefits" convention for text documents, but I see a fair amount of superiority over Sweave/LaTeX for short documents and literate programs.
I see that most people use embedded LaTeX for expressions in various markdown implementations. Is this canonical or is this the result of 'improved' implementations such as Pandoc, etc.?
Btw, OP, you got your $2.99 - royalty from me because I want yet another reason to tell people there is no reason for them to have their laptops open in meetings.
I have very high hopes for an R + LightTable integration.