I am tired of finding why Tinn-R cannot work perfectly under windows7 with 64-bit
I searched Google for other R editor.
JGR is also good but a little bit burdensome and in my case it got frozen when start rattle.

I found Rstudio released recently is also pretty good!
http://www.rstudio.org/

It's fast and work perfectly under windows 7 with 64-bit and showing your data in work place as matlab and JGR does.
The only drawback is it can show spicial color for standard function.