I have been using RStudio for a few months now and would recommend it. Some of the features I like are:
1. I can organise scripts much more easily
2. Installing libraries and accessing+browsing help files is much more interactive
3. Using the tab key to browse data file names and scripts in working directory during scripting
4. Manipulate function for plot interactive controls (
http://www.rstudio.com/ide/docs/advanced/manipulate)
5. Easier to specify plot resolution and size when exporting
6. list of active workspace objects and variables with a summary of data type and contents
Cheers,
Varun