I've been a huge fan of TextWrangler for years. I use it for all of my coding (including with R), for taking notes during meetings, for taking notes on articles, and more. It's my most frequently used application. But, I'm ready for a change and am going to give Sublime Text 3 a try. It seems very powerful, relatively light, and incredibly extensible.
I recently installed Sublime Text 3, added Package Control, and installed some R packages to try out. I'll give it a try for the next three weeks and see what I think. It might be time to say farewell to TextWrangler.