[R] best editor for .R files

[Angel]

Which is the best editor for .R files?

I currently use kate on my linux as it has R highlighting and allows me to
split the window into two: in one I edit the .R file and in the other I have
a shell so I run R and can easily  copy and paste the code. There are some
features that I don't like and I am having a look on some alternatives.
I've heard wonders of emacs with ess but I am a little bit frightened of the
steep learning curve.

What do the R experts use or would recommend using?
Both linux and/or windows alternatives are welcomed.
I guess it would much depend on the particular needs/preferences of each
user but I would like to know which are the most commonly used editors.
Thanks,
Angel